DIAMOND BAR, Calif. (AP) — Los Angeles County fire officials say a malfunctioning catalytic converter on a vehicle is believed to have caused brush fires that threatened homes in the city of Diamond Bar.

Inspector Frederic Stowers says a malfunctioning catalytic converter can spit out hot metal shavings which would account for the multiple ignition points of the blaze late Tuesday morning.

Stowers says the 50-acre blaze is 60 percent contained but there's very little fire activity and firefighters are in the mop-up process.

Four civilians suffered minor injuries from smoke inhalation and a firefighter suffered heat stress.

No structural damage has been confirmed.

The 1,600 students at Diamond Ranch High School were safely sheltered in a gym as the fire swept by. They are now being dismissed.