A small fire was burning on the Santa Catalina Mountains Thursday evening.
Approximately one acre has burned so far, said Heidi Schewel, public affairs officer for the U.S. Forest Service. She added it is burning in the vicinity of Finger Rock Canyon.
No structures are being threatened by the fire, Schewel said.
It was possibly caused by a lightning strike but the official cause is being investigated. Storms were expected to move through the area Thursday evening, according to forecasts by the National Weather in Tucson.
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Officials are monitoring the fire and will reevaluate if action needs to be taken.Â
Monsoon photos 2018
Photos: Monsoon 2018 and other rainstorms in Tucson
Monsoon Storm Over Tucson AZ
Monsoon storm on August 16, 2018 over Tucson AZ viewed from the foothills
Monsoon lightning Tucson 8-22-18
Monsoon storm over downtown Tucson
Monsoon Storm Rolls in Over Sunset
Monsoon Covers Sunset Over Tucson
After the monsoon
Cows grazing
"Twister i n the Clouds"
Sun's shadow on the clouds
Hurricane Rosa
A man who said his backyard was flooded tries to dislodge debris from a wash behind homes at N. Cerius Stravenue and W. Calle Maverick during rain from the remnants of Hurricane Rosa in Tucson, Ariz., on Oct. 1, 2018.
Hurricane Rosa
Workers from the Tucson Dept. of Transportation load sandbags for residents during rain from the remnants of Hurricane Rosa in Tucson, Ariz., on Oct. 1, 2018.
Hurricane Rosa
A tow truck driver eyes a flooded section of Silverbell Road at W. Benjamen Road during rain from the remnants of Hurricane Rosa in Tucson, Ariz., on Oct. 1, 2018.
Hurricane Rosa
Steady rain today brought puddles to reflect the beauty in Brandi Fenton Memorial Park on the University of Arizona campus on October 1, 2018 in Tucson, AZ.
Hurricane Rosa
Steady rain today brought puddles throughout town including this intersection at University Blvd and Cherry Ave. on the University of Arizona campus on October 1, 2018 in Tucson, AZ.
Tucson monsoon 2018
Grocery shoppers hustle to and from their cars as a late-season weather system brought rain to the city and surrounding areas on Sept. 19, 2018, as seen in Oro Valley, Ariz.
Tucson monsoon 2018
Students try their best to above rain runoff in the streets around the University of Arizona campus as a late-season weather system brought rain to the city and surrounding areas on Sept. 19, 2018, as seen in Tucson, Ariz.
Tucson monsoon 2018
A man tries to clear collected rain runoff in the streets around the University of Arizona campus as a late-season weather system brought rain to the city and surrounding areas on Sept. 19, 2018, as seen in Tucson, Ariz.
Monsoon 2018
A widespread monsoon storm produced steady rain all afternoon but no rainbows in the sky, however at ground level a pedestrian with a rainbow umbrella crosses Scott at Pennington, Wednesday September 19, 2018, Tucson, Ariz.
Cienega vs Cholla
Lightning stabs the night just to the east of the football field at Cholla High where monsoon storms with postponed the Chargers game with Cienega and all  Friday, August 24, 2018, games. The Cholla/Cienega game was moved to Saturday at 9 a.m. at Cholla, Tucson, Ariz.
Pueblo vs. Tucson high school football
Despite threatening clouds overhead, Matthew Sanchez marches on with his brass contribution in the Tucson Marching 100 band just prior to a lightning delay at the Pueblo vs. Tucson high school football game at Tucson High Magnet School, 400 N. 2nd Ave., on Aug. 24, 2018, in Tucson, Ariz.
Cienega vs Cholla
The onset of the rain drives the last fan to seek shelter from the storm, after earlier lightning strikes had driven the crowd for Cienega's game at Cholla High School to the safety of the school gym, Friday, August 24, 2018, Tucson, Ariz.
Monsoon 2018
Johnny Romero fights the wind and rain to hold down a pop-up tent outside a friend's house in Menlo Park near Sentinel Peak on Aug. 22, 2018, in Tucson, Ariz.
Monsoon 2018
Some people just couldn't wait any longer as traffic was tied up for hours on Thornydale Rd. just south of Overton Rd. following a heavy rainstorm on August 22, 2018 in Tucson, AZ. Several washes run across a long stretch of Thornydale from Carter Farms north past Linda Vista Rd.
Monsoon 2018
A bolt strikes just north of downtown, part of one of dozens of localized monsoon storm cells that moved through the area dumping rain, winds and lightning, Wednesday, August 22, 2018, Tucson, Ariz.
Monsoon 2018
A bolt strikes just north of the University of Arizona, part of one of dozens of localized monsoon storm cells that moved through the area dumping rain, winds and lightning, Wednesday, August 22, 2018, Tucson, Ariz.
Uprooted Tree
One of the dozens of trees that were blown over at Sunset Point Wednesday August 22nd, 2018 by a powerful monsoon storm that uprooted dozens of full sized trees as hail and rain pelted the northwest near Cortaro Farms and Camino de Oesta.
Fallen Tree
A red Mustang is covered by a fallen pine tree at Sunset Point Wednesday August 22nd, 2018 after the Northwest was hit by a powerful monsoon storm that uprooted dozens of full sized trees, broke off branches of other and peppered the area with hail.
Clouds over "A" Mountain
People gather to watch a dramatic sunset as clouds roll in over the Tucson Mountains on August 20, 2018 in Tucson, AZ.
Clouds over "A" Mountain
People gather to watch a dramatic sunset as clouds roll in over the Tucson Mountains on August 20, 2018 in Tucson, AZ.
Clouds over Tucson
Clouds swirl across the city and the Santa Catalina Mountains during a dramatic sunset over Tucson on August 20, 2018 in Tucson, AZ.
Monsoon 2018
Monsoon clouds color the sky around the sun as it sets behind Brown Mountain in Tucson Mountain Park, Wednesday, August 15, 2018, Tucson, Ariz.
Monsoon 2018
The setting sun has just enough left to spark a rainbow in monsoon clouds high over the Tucson Mountains , Wednesday, August 15, 2018, Tucson, Ariz.
Monsoon 2018
A bolt hits in the Santa Rita Mountains southeast of Tucson as monsoon storms surround the valley on August 7, 2018.
Oro Valley
Pusche Ridge
Lightning U of A 8-11-18
Welcome to Tucson students.
Pusch Ridge Oro Valley
Clouds over the mountain
Lightning at Night
Storm over Tucson 8/1/18
Zap!
Lightning, downtown Tucson.
Monsoon Sky
Monsoon storm moving in over the Catalinas
Fire Sky
Monsoon sky at Stone Canyon Club
Pretty in Pink
Oro Valley sky
Hot Weather
With the help of Jaleesa Lopez, 10, far right, his sister, Orlando Celaya, 1, sprays his brother, Marsaleno Oliver, 7, while cooling off in the splash pad at Catalina Park on July 23, 2018. Jessica Lopez, their mother, said the air-conditioning in the house broke down and she brought her kids to the splash pad to cool off as the outdoor temperature soared beyond 105-degrees.
Tucson monsoon sunset
A young couple takes in monsoonal cloud sunset over the Tucson Mountains as they endure gusty updrafts at a lookout on Sentinel Peak on July 18, 2018, in Tucson, Ariz.
Monsoon 2018
Monsoon 2018 takes a breath, things kind of quiet on the weather front just after sunset over the Father Kino statue at Kino and 15th St., Wednesday July 11, 2018, South Tucson, Ariz.
Monsoon 2018
Clouds put on a show today with a variety of ever-changing shifting, rolling and scattering on July 18, 2018 in Tucson, AZ.
Monsoon 2018
Clouds put on a show today with a variety of ever-changing shifting, rolling and scattering on July 18, 2018 in Tucson, AZ.
Tucson Monsoon 2018
A flood area sign lays in monsoon rain runoff on South Plumer Avenue in midtown on July 12, 2018, in Tucson, Ariz.
Monsoon 2018
While monsoon storm clouds build over the Santa Catalina mountains, workers assemble a new crane on-site for construction on The Mark student housing near Broadway Boulevard and Park Avenue on July 10, 2018, in Tucson, Ariz. A fire crippled one existing crane and damaged a second, larger one.
Tucson Monsoon 2018
Justin Grob, 16, goes for a jaunt in the monsoon rain runoff along South Plumer Avenue in midtown on July 12, 2018, in Tucson, Ariz.
Tucson Monsoon 2018
A motorists decides better of it by turning around at the Arroyo Chico Wash along South Plumer Avenue in midtown on July 12, 2018, in Tucson, Ariz.
Tucson Monsoon 2018
A City of Tucson worker stands a flood area sign at the Arroyo Chico Wash and South Plumer Avenue in midtown on July 12, 2018, in Tucson, Ariz.
Tucson Monsoon 2018
A motorist takes their chances by sending the rushing Arroyo Chico Wash at Plumer Avenue after an afternoon monsoon storm in midtown on July 12, 2018, in Tucson, Ariz.
Monsoon 2018
Droplets invert the image of a saguaro at Saguaro National Park East along Freeman road during a monsoon storm, Tuesday July 10, 2018, Tucson, Ariz.
Tucson monsoon
Lightning and Ocotillo meet as a late evening storm moves across Oro Valley towards the Tucson Mountains on July 8, 2018 north of Tucson, AZ.
Monsoon 2018
Union Pacific train derailment on the east side of I-10 just north of Twin Peaks Road in Marana on July 10, 2018.
Tucson Monsoon 2018
Vehicles negotiate the water flooding down the washes and sides of Thornydale Rd between Cortaro Rd. and Hardy Rd following a monsoon storm that swept down the westside of Oro Valley and Tucson, AZ on July 10, 2018 .
Monsoon 2018
Union Pacific train derailment on the east side of I-10 just north of Twin Peaks Road in Marana on July 10, 2018.
Monsoon 2018
Motorists are met with driving rain West Ina Road near La Cholla Blvd. on July 10, 2018, in Tucson, Ariz. Strong monsoon storms pummeled the northwest side.
Tucson Monsoon 2018
Two men carry on their conversation under a ramada as a monsoon cell opens up around them near 6th Avenue and Bilby Road on July 5 2018, in Tucson, Ariz.
Monsoon 2018
A highly localized downpour in the foothills of Santa Catalinas just north of downtown as several small but intense cells dropped rain and high winds on the area during the first monsoon storm of the season, Wednesday July 5, 2018, Tucson, Ariz.
Sculpture on overpass
Tucson Dept. of Transportation workers examine a large light sculpture that fell onto the southbound lanes of the Kino Overpass at 22nd Street during monsoon activity on July 5, 2018.
Tucson Monsoon 2018
Motorists encounter the season's first monsoon rainfall near Nogales Highway and Los Reales Road on Tucson's southside on July 5 2018, in Tucson, Ariz.
Tucson Monsoon 2018
A monsoon storm cell brings rain to Tucson's southside, seen here at Super Carniceria y Pescaderia "El Ranchito" near 6th Avenue and Bilby Road on July 5 2018, in Tucson, Ariz.
Hot Tucson
Mike Livermore lowers his two-year-old grandson Michael Baker for a brief cooling-off in the stream near the Reid Park pond on July 5 2018, in Tucson, Ariz. Today is expected to be the hottest day of the year in Tucson.
Tucson Monsoon 2018
A monsoon rain cell drops somewhere in Tucson, as seen from near 36th Street and Kino Parkway on July 5, 2018.
Tucson Monsoon 2018
A pedestrian sprints through monsoon rainfall on Park Ave. near Irvington Road, Tucson, on July 5, 2018.
Sculpture on overpass
Tucson Dept. of Transportation workers examine a large light sculpture that fell onto the southbound lanes of the Kino Overpass at 22nd Street during monsoon activity on July 5, 2018.
Sculpture on overpass
Tucson Dept. of Transportation workers examine a large light sculpture that fell onto the southbound lanes of the Kino Overpass at 22nd Street during monsoon activity on July 5, 2018.
Sculpture on overpass
A large light sculpture that decorates the Kino Overpass at 22nd Street fell into the southbound lanes during monsoon activity on July 5, 2018.
Contact Star reporter Shaq Davis at 573-4218 or sdavis@tucson.com
On Twitter: @ShaqDavis1
Shaq Davis
Reporter
