As firefighters continued their search through the stricken area for victims, federal investigators indicated that they would be looking at a range of contributing factors – including maintenance records, pressure conditions, and human factors.
Four people were killed in the blast and fire and at least 50 people were injured, according to local public safety officials.
As firefighters continued their search through the stricken area for victims, federal investigators indicated that they would be looking at a range of potential contributing factors. These include the pipeline's maintenance record, pressure conditions in the 30-inch-diameter line at the time of the explosion, and at the warning systems the line's owner – Pacific Gas and Electric – had in place to alert technicians of problems in the line.
Officials also will be looking into the role human factors may have played, ranging from training to PG&E's response time in addressing complaints some residents say they lodged about gas they smelled before the blast.
It didn't take long to spot what could become one hefty piece of evidence in the blast.
At a briefing Friday night in San Bruno, Christopher Hart, vice-chairman of the National Transportation and Safety Board, described coming across a large portion of the gas-transmission-line pipe in a street "some distance" from the large crater where the blast occurred.