Los Angeles, California - Thousands of people were being told to flee a wildfire spreading in southern California on Tuesday, as strong winds fanned the flames.

Around 5,700 people were urged to leave areas threatened by the blaze, which erupted on Monday around lunchtime and had engulfed 2,200 acres by the following morning.

The Highland Fire, in the countryside southeast of Los Angeles, has already leapt one highway and destroyed three buildings. Six other structures were known to have been damaged.

More than 300 firefighters were tackling the flames on the ground, assisted by aircraft that were dropping water on the blaze.

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Maggie Cline de la Rosa of Cal Fire in Riverside County told AFP crews were battling strong winds and difficult terrain.

"The biggest issue right now is high winds," she said. "It is also topography driven - lots of valleys and gulches that the fire gets down into and gets established. And they're trying to keep it... from crossing the highway again."

The National Weather Service reported that gusts of up to 30 MPH could be expected during the day.

So-called Santa Ana winds are a common feature of autumn in the southwestern United States and fuel fire risks in an area that is prone to outbreaks.

A very wet winter, followed by an unusually moist year have created an explosive growth of vegetation in large swaths of California after years of drought.

Experts had warned that this vegetation could dry out and provide fuel for fires, which are a natural part of the climatic cycle.

Scientists say human-caused climate change is affecting our weather patterns, making dry periods drier and longer, and wet periods more intense.