An explosion and fire ripped through a gasoline processing unit at an Exxon Mobil refinery in Torrance, California, near Los Angeles on Wednesday, slightly injuring four workers and shattering windows of surrounding buildings, authorities said. Investigators were trying to determine the cause of the blast, which occurred shortly before 9 a.m. PST (12 p.m. ET), but there was no evidence of foul play, according to Torrance Fire Captain Steve Deuel. Deuel said a small ground fire following the explosion was quickly extinguished.