LOS ANGELES –  Remnants of a tropical storm helped firefighters gain ground on a 4,180-acre blaze in the San Gabriel Mountains northeast of Los Angeles, with containment doubling Wednesday to 48 percent.

Crews have been working on steep slopes in the Angeles National Forest since Sunday to put out the fire in chaparral that hasn't burned in 15 or 20 years, according to fire officials.

They got some relief from Tropical Storm John, which brought light rainfall, increased humidity and cooler temperatures.

Angeles National Forest Spokesman Nathan Judy said the fire has been stopped along the southern containment line where structures were threatened and permanent residents of the small community of Camp Williams will be allowed to return to their homes Thursday morning.

Firefighters were concerned the moist air would lead to lightning and more fires, but Judy said that hasn't been a problem.

The blaze was expected to be fully surrounded Sept. 13. Nearly 1,300 firefighters were on hand despite the treacherous terrain and slopes between 30 percent and 80 percent. At least five firefighters have sustained minor injuries.

A 25 percent chance of thunderstorms continues in the area through Thursday, said Stuart Seto, a National Weather Service specialist.

The moisture was the last hurrah from Tropical Storm John, which got churned up in a low-pressure system approaching from the north, Seto explained.

Besides the rain, nine firefighters from Australia and New Zealand arrived Wednesday to join fire crews and get a firsthand look at tools and techniques being used to battle the blaze, said Los Angeles County fire Capt. Roland Sprewell.

It's like a firefighter exchange program, he said.

"Our fire problems are very similar, although fuel types and fuel models are different, so what we have to teach them is how we apply the various tools, from aircraft to our hand crews to our dozers," Sprewell said.

Southern California also uses an incident command system that serves as a model across the nation, he said. When a fire occurs, an organization is immediately put into place so when firefighters and equipment show up at base camp, they find a mini city ready for them, he explained.

By the weekend, a high-pressure system should arrive and clear the skies, raise the temperatures and lower the humidity, Seto said.

On the fire lines, crews have eight air tankers, 10 helicopters, 68 engines, eight dozers and 11 water tenders.

Firefighters were still looking for a cause. A burned car was found in the area, but it was unknown if the vehicle caused the fire or was just destroyed by it.

As many as 12,000 people were asked to evacuate the area over the busy Labor Day weekend. About 25 residents of the nearby community of Camp Williams refused to leave.

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Dillon reported from Camp Williams.