Up to 2,000 people were ordered out of their homes after the fire, which ravaged about 1,700 acres in the suburbs, according to police in Azusa, just north of Los Angeles.
Several schools and colleges were also evacuated in Azusa and Glendora. The blaze damaged at least three homes, according to local media.
Glendora police detained three men who allegedly set a campfire which sparked the blaze, shortly before 6:00 am (1400 GMT). The long pall of smoke drifted across toward downtown as dawn broke.
“They are being cooperative … one has made an admission and has admitted to setting this fire,” Glendora police chief Tim Staab told reporters at a late morning press conference about the fire.
The three, one of whom is homeless, are being held on $20,000 bail each, he said.
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