The Williams Fire as seen Sunday. (Jim Staley/Flickr)

The Williams fire, north of Glendora and Azusa in the Angeles National Forest, has charred 3,600 acres since starting Sunday afternoon. The cause still is under investigation. Firefighters used controlled burns to help secure some perimeters Monday night, making good progress, fire officials said.

Four air tankers, 10 helicopters, 40 engines and five water tenders have been involved in the operation.

Fire officials said 25 people have ignored orders to evacuate nearby Camp Williams and the canyon.

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