Nearly 2,000 residents were evacuated and at least two homes burned in a wildfire that started when three people tossed paper into a campfire in the dangerously dry and windy foothills of Southern California's San Gabriel Mountains.

Embers from the fire fanned by the Santa Ana winds quickly spread into neighbourhoods below, where residents were awakened in the pre-dawn darkness and ordered to leave.

The three suspects, all men in their 20s, were arrested on charges of recklessly starting the fire that spread smoke across the Los Angeles basin and cast an eerie cloud all the way to the coast.

More than 700 firefighters were on the scene, along with 70 engines and a fleet of helicopters and air tankers dropping water and retardant.