LA HABRA, Calif. (AP) — An explosion and fire possibly caused by a dust buildup at a Southern California metal-polishing shop injured 11 people Tuesday, including two men who were critically burned, fire officials said.

The blast occurred in an overhead duct system shortly before 10 a.m. in an industrial area of La Habra, a Los Angeles suburb. It took more than 50 firefighters about 40 minutes to douse the resulting fire.