Dramatic photos help BP blast investigators pinpoint cause

06:16 PM CDT on Thursday, April 7, 2005

By Doug Miller & Reggie Aqui / 11 News

Reggie Aqui's 11 News report

CSB news conference

Doug Miller's 11 News at 6 report

Federal investigators are releasing more details about the probe into what caused last month's deadly explosion.

KHOU-TV

Damaged trailers

We saw the chaos from the sky, heard from witnesses standing nearby. Now, we are beginning to see it from the ground. CSB and OSHA investigators have studied dramatic scene photos, talked with survivors and determined that excess pressure forced liquid hyrdocarbons and vapor up a 100-foot stack, spewing like a geyser.

Witnesses say it happened as an isomerization unit that had been shut down for routine maintenance was restarted.

"They then saw the liquid and vapor fall to the ground. Shortly afterwards, the hydrocarbon ignited and, within seconds, there was a powerful explosion," said Bill Hoyle the chief investigator for the U.S. Chemical Safety Board.

That explosion, and a second that followed, killed 15 people and injured more than 100.

The exact ignition source for the blast remains a mystery but i nvestigators are examining 30 cars and trucks found near the blast site. They want to know if one or more of those vehicles ignited the vapors.

Witnesses that day told us about a truck driver. "When the guy's truck turned off, he tried restarting it. When they told him not to, he kept on trying to restart it and it ignited," said the witness.

OSHA's still not sure -- still examining whether a truck sparked the explosion -- still trying to determine why excess pressure built up in the unit that showered the area with flammable hydrocarbons.

They also want to know why workers were in a nearby trailer during the potentially dangerous process of restarting the unit.

As they search for answers, federal investigators say the blast site remains hazardous because of hanging debris and possible chemical residue on the equipment. They are wearing masks as a precaution and are working with BP to remove those hazards.

Investigators expect to remain on the site for several more weeks.