No Jacobs officials would confirm that those killed were Merit employees, but a BP spokesman says the refinery’s isomerization unit was undergoing “major annual maintenance” at the time of the explosion. “Everyone knows that this is turnaround season in the industry,” says Scott Dean, Chicago-based spokesman for BP. Officials had no information on which other contractors may have suffered losses.

The unit is one of 30 at the refinery, which sprawls over 1,200 acres. About 3,300 people were at the plant, including 2,200 contractor employees and 1,100 BP employees, says Hugh Depland, another BP spokesman. With capacity to refine 460,000 barrels per day of crude oil, the plant is capable of providing 3% of U.S. gasoline supply. It represents 30% of BP’s North American refining capacity.

The fire, which sent a smoke plume more than 3,000 ft into the sky, was extinguished in just over two hours. Investigators have ruled out terrorism as a cause, but will say nothing more for the present. A team of investigators is scheduled to arrive today, March 24. Production is continuing at the refinery, but contractors will have a safety stand-down, returning to work on Monday, say BP officials. No estimate of cost or time required to repair the damage has been announced.