Four workers suffered minor injuries Wednesday in an explosion that rocked an ExxonMobil oil refinery south of Los Angeles, the company said.
The blast, which was followed by a large smokestack flare, poured ash down onto local neighborhoods, while local schools were temporarily ordered to keep students inside, media reports said.
But the company downplayed any pollution threat at the refinery in Torrance, 20 miles (32 km) south of downtown LA. "No harmful emissions have been detected," it said in a statement.
"All personnel have been accounted for. Four contractors have been taken to Long Beach Medical Center for evaluation for minor injuries," it added.
Aerial footage of the refinery showed some areas of twisted metal and some vehicles covered with debris and ash. One vehicle appeared to have a collapsed roof.