AZUSA (CNS) — A fast-moving brush fire in the Angeles National Forest is 40 percent contained Friday morning after scorching about 240 acres in the Morris Dam north of Azusa. It has prompted avacuation orders. According to the U-S Forest Service ... five helicopters and two air tankers will be assigned to the firefighting effort Friday ... along with ground crews ... who'll be toiling in dry conditions and temperatures of more than 100 degrees.

"A very robust air and ground attack is holding back further spread," Angeles National Forest Fire Chief Robert Garcia said. "But tough days ahead in some of the steepest terrain in the Angeles, combined with a heat wave of 100-degrees-plus. Please give thanks to your firefighters."

The fire was reported about 1:20 p.m. Thursday near the 9500 block of North San Gabriel Canyon Road, also called Highway 39, according to the Los Angeles County Fire Department, which was assisting Angeles National Forest crews.

The blaze grew from about 25 acres to 240 acres in less than two hours, first forcing evacuations of campers in the West Fork area of the forest and soon other areas of the forest, according to the Glendora Police Department and the U. S. Forest Service.

"This evacuation is not in a developed residential area but it's in some of the recreation areas in the forest," Marc Peebles, public information officer with California Incident Management Team 13, told a CBS2 reporter at the scene late Thursday afternoon. "Essentially the evacuation area is on Highway 39, north of Old San Gabriel Canyon Road.

"The Crystal Lake recreation area has been evacuated, the West Fork and East Fork recreation area has been evacuated, and it's mainly visitors recreating in the forest. There's some ... special use cabins up there, as well at the Coldbrook Campground and the San Gabriel off-highway vehicle staging area."

Highway 39 is closed to all traffic through at least Sunday, the Azusa Police Department said, adding non-residents will not be allowed to continue beyond the El Encanto Restaurant.

About 250 Angeles National Forest firefighters and about 100 Los Angeles County firefighters were battling the blaze on the ground, with more than a dozen aircraft also working to quell the flames.

"It's very, very steep rugged terrain. Some of it is near vertical, especially right off of Highway 39 here," Peebles said Thursday. "It's thick brush, it's hot, it's dry, it's steep. We've got a little bit of breeze that you see ... The fire doesn't appear to be terribly wind-driven at this point. It's mainly driven by slope and heat."

VIVA Rescue, a nonprofit organization specializing in rescuing horses, offered in a Twitter post to help evacuate animals — "equines, livestock and domestic pets" — from the forest. Anyone needing its help was urged to send a text to 310-808-5943.