San Francisco, Aug 3 (IANS): More than 1,300 firefighters, backed by helicopters and water-dumping planes, were battling a massive wildfire in Southern California that has forced thousands of people from their homes east of Los Angeles.

Dubbed "Apple Fire", the state's first major wildfire of the year began on July 31 as two adjacent blazes in Cherry Valley, an area near the city of Beaumont in Riverside County, reports the BBC.

It has since stretched out to 20,516 acres, San Bernadino National Forest said in a tweet on Sunday.

Parts of the blaze are on steep, rugged hillsides, making it hard for fire engines to reach.

Around 8,000 residents have been asked to evacuate the area.

Images show flumes of smoke filling the sky over the mountainous region.

In a tweet, the National Weather Service said some smoke had blown east to Phoenix, Arizona - nearly 482 km away.

The government body said the blaze had been fuelled by high temperatures, low humidity and dry vegetation in the area.

The US Forest Service told the Riverside Press-Enterprise, a local newspaper, that because the fire was on rugged terrain, it was dangerous for firefighters to try and surround it.

"We don't want to put fire-fighters in a dangerous situation," said spokesperson Lisa Cox.

"It's burning in a straight line up a mountain."

California Governor Gavin Newsom announced on Sunday that the state has secured a grant from the Federal Emergency Management Agency to help ensure the availability of resources to fight the wildfire, reports the Los Angeles Times.

The grant will also assist local and state agencies responding to the fire to apply for reimbursements for up to 75% of fire suppression costs.