SAN MATEO, Calif. – A gas pipeline that ruptured and caused a deadly explosion in a Northern California neighborhood showed no signs of external corrosion and wasn't dented or leaking, federal accident investigators said Tuesday.
Investigators with the National Transportation Safety Board have yet to determine what caused the transmission line to rupture on Sept. 9, killing eight people and destroying dozens of homes.
They found no physical evidence of a pre-existing leak in the pipe pieces, nor did they see dents or gouges suggesting that someone struck the pipe with excavation equipment.
Rep. Jackie Speier, a California Democrat who represents the San Bruno area, is planning to hold a Tuesday morning news conference, along with other local officials, after being briefed on the report. The NTSB findings are preliminary and come after investigators tested numerous segments of the 30-inch line.
The explosion and ensuing inferno torched nearly 15 acres of 1960s-era suburban homes in the hills overlooking the San Francisco Bay. Dozens of people were injured in the blast, and some victims are still in hospital burn units.
The ruptured pipeline's operator, Pacific Gas & Electric, called the pipe "high-risk" in 2007 and received permission from the California Public Utilities Commission to bill ratepayers to upgrade the pipeline. But they dropped the improvement plans the next year.
The NTSB also is investigating why it took PG&E crews nearly 90 minutes to deploy manual valves to stop the flow of gas into San Bruno the night of the explosion.