Witnesses saw truck "rev up and race" before recent Texas oil refinery blast

Witnesses say a truck was idling near the scene of an explosion at a Texas refinery which killed 15 and injured over 100 others on March 23, according to U.S. Chemical Safety and Hazard Investigation Manager Bill Hoyle.

"Witnesses saw vapor in the area of the truck and observed the engine begin to rev up and race," Hoyle's statement said. "This behavior by a diesel engine indicates the presence of a flammable atmosphere entering the air intake. A driver reported trying to shut off the engine but was unable to do so." Hoyle's statement continued, "There are multiple possible sources of ignition in an operating refinery unit and we have made no determination about the ignition source at this time."

The investigation has been delayed by BP and Occupational Safety & Health Administration officials, who are trying to preserve evidence at the site for their investigation. They are also concerned about further injuries from hazards left over from the explosion, such as falling debris and unstable structures. The Environmental Protection Agency also detected benzene in the atmosphere over the plant, which was treated with a layer of foam.

BP has retained control of the plant since the March 23 accident. Police arrived quickly the day of the explosion, but left after the initial emergency was over.

"Our officers could respond over there, but they don't have a clue," Texas City police Sgt. Curtis Pope told the Houston Chronicle. "The fact is they have chemical and equipment hazards. We don't know the chemicals."