100-acre Gulch fire north of Azusa is 0% contained in Angeles National Forest

SAN GABRIEL MOUNTAINS, CA - AUGUST 29: Fire crews are working to contain a brush fire burning near Mile Marker 21 along San Gabriel Canyon Road near the San Gabriel Dam. According to the Angeles National Forest, the Gulch Fire has burned up to 100 acres (CBS Los Angeles) on Monday, Aug. 29, 2022 in San Gabriel Mountains, CA. (Gary Coronado / Los Angeles Times)
Fire crews work to contain the Gulch fire near San Gabriel Dam on Monday. (Gary Coronado / Los Angeles Times)

A brush fire that started in the Angeles National Forest north of Azusa grew to 100 acres by late Monday afternoon.

The Gulch fire is burning upslope near San Gabriel Dam and heading west-northwest, forest officials said. Highway 39 is closed north of Azusa, and there is no access to San Gabriel Canyon.

The blaze remained at 100 acres and was 0% contained Monday night, forest officials said.

A second, smaller fire burned near Morris Dam, the Los Angeles County Fire Department said.

Dana Dierkes, an Angeles National Forest spokesperson, said the smaller fire is considered part of the Gulch fire.

The blaze was first reported just before noon burning in heavy vegetation, but with no structures threatened. Power lines were a concern for firefighters, and one firefighter sprained his ankle, according to dispatch reports.

The fire's cause remained under investigation as of late afternoon, Dierkes said.

Firefighters were aggressively working to contain the fire, with more than 200 personnel assigned along with four night-flying helicopters, forest officials said.

Forest visitors should be mindful and take steps to prevent fires, Dierkes said. Any campfires or grills should be handled carefully and completely extinguished after use.

Those towing trailers or other objects should be careful not to drag tow chains on the roadway, as they can cause sparks that ignite fires, Dierkes said. Drivers should also be careful not to stop on the side of the road because a vehicle's hot undercarriage can ignite dry grass.

The blaze comes as California braces for what's expected to be the summer's longest and most intense heat wave.

The National Weather Service has issued an excessive heat watch for much of Southern California, as temperatures are expected to hit triple digits this week and into Labor Day weekend.

Meteorologists are warning of elevated fire weather risk from Wednesday through next Tuesday.

This story originally appeared in Los Angeles Times.