Nearly 2,000 residents were evacuated and two homes burned in a wildfire that started when three people lit a campfire in the dry foothills of Southern California's San Gabriel Mountains.
Embers from the fire fanned by winds quickly spread. Residents were woken at dawn and ordered to evacuate.
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.
One resident suffered minor burns.
Between 1,700 and 2,000 residents were evacuated and the order included 880 homes in Glendora and the neighbouring foothill city of Azusa.
Many residents, some wearing masks, used garden hoses to wet the brush around their houses.
At least two-and-a-half square miles of dry brush were charred in the wilderness area about 25 miles northeast of downtown Los Angeles.