Hundreds of firefighters have stepped up efforts to contain a wildfire that has destroyed more than 3,200 hectares near Los Angeles, Xinhua reported.

Since its outbreak Thursday, the Crown Fire has damaged several structures, including a family home, two garages, a building and a hay barn, the Los Angeles County Fire Department (LACFD) said Friday. About 750 firemen were deployed.

Soaring temperatures coupled with breezy conditions posed a challenge to firefighters, it said.

They were working to protect major power lines in the area that serve southern California, said Michael Bryant, LACFD deputy chief.

The cause of the fire was under probe, but it could have been sparked by workers working on a tire rim, he noted.

'They were using a hammer to try to get the bolts loose, and that's what the investigation is really focusing on right now,' he said, adding that there was still no confirmation that the workers started the blaze.

With the Crown Fire threatening power lines in the northern reaches of Los Angeles County, the Department of Water and Power asked residents Friday to reduce their power usage -- as long as it does not compromise their health or safety.

A DWP spokesman said the utility has minimized power imports on a transmission line that passes through the fire-threatened Leona Valley, and is generating power at closer plants to deliver energy to the city.

A series of brush fires have been sweeping parts of southern California in the past few days.