By Jay Parsons
The Dallas Morning News
Copyright 2007 THE DALLAS MORNING NEWS
 
DALLAS — Federal investigators headed back to Washington on Saturday without releasing many clues from their review of Wednesday's gas explosions near downtown Dallas that injured two and rocketed flaming gas cylinders onto highway overpasses.

U.S. Chemical Safety Board inquiries "are long, painstaking investigations that can take more than a year to complete," said board member William Wark.

The fire started with a leak while a truck was delivering acetylene gas to the Southwest Industrial Gases on Industrial Boulevard, the safety board investigators said.

On Thursday, a Southwest Industrial employee told The Dallas Morning News the truck driver told him, "I hooked up something wrong."

Employees said the truck driver - from Western International Gas & Cylinders, outside Houston - was handling the canisters when the fire started.

The federal investigators would not say Saturday whether human error or a mechanical failure started the fire. They said only that the blaze started in the back of the 18-wheeler's trailer during delivery and that it spread rapidly.

"We're going to try to establish what the root causes were," said lead investigator Robert Hall. "We just don't know at this time. ... We're really hampered because the truck has been obliterated."

The chemical safety board, with a setup similar to the better-known National Transportation Safety Board, investigates industrial chemical accidents but has no regulatory power.

Mr. Wark said investigators finished collecting evidence at the site Saturday. Analysis starts upon returning to Washington, he said. Mr. Wark said they plan to come back to Dallas periodically.

Mr. Hall said the incident should remind cities to be cautious when zoning industrial facilities that handle flammable gases. Wednesday's explosions happened near the intersection of Interstates 30 and 35E.

"That's really a local issue," Mr. Hall said, "and local officials need to consider the risk."