SANTA CLARITA >> A small brush fire in Santa Clarita on Thursday afternoon quickly ballooned into a 20-acre blaze that destroyed one outbuilding and threatened more than a dozen structures, the Los Angeles County Fire Department reported.

The fire broke out just after 1:41 p.m. in the 23000 of the The Old Road in Newhall, near the Newhall Church of the Nazarene just south of the entrance to Towsley Canyon Park, Inspector Richard Licon said.

It quickly progressed into a three-alarm fire with 20 acres and one outbuilding burned, county fire officials reported. News reports described the ruined structure as a building in a paintball park

The wildfire had grown to 20 acres by 4:30 p.m. with 20 percent containment, authorities said. Fifteen structures along The Old Road were threatened.

“Forward Progress Stopped via aggressive ground and air resources,” the Los Angeles County Fire Department tweeted.

More than 225 firefighters were working in sweltering heat to combat the blaze, Licon said.

• Photos: Smoke bomb used at paintball game starts fire

By midafternoon, temperatures in the area had reached 95 degrees, with 23 percent humidity, according to The Weather Channel, with 12 mph southwest winds.

Additional firefighters were called in, as well as water-dropping helicopters and fixed-wing aircraft, to battle the blaze that’s being called the Towsley fire.

The following road closures were in effect, according to the Los Angeles Sheriff’s Department, Santa Clarita Station:

• The Old Road was closed southbound at Calgrove Boulevard.

• The Old Road was closed at the Church of the Nazarene.

• Traffic along Interstate 5 may be impacted.

The U.S. Post Office, the Newhall Church of the Nazarene and the paintball park, named Field of Fire Paintball Adventures along The Old Road were evacuated, the Sheriff’s Department reported. There were no further evacuations.

The cause of the wildfire was unknown.

A short time later, two other fires broke out further north along the 5 Freeway, burning about 10 acres of brush near Pyramid Lake.