The group headed by the National Transportation Safety Board investigating the Sept. 9 natural gas pipeline rupture and explosion that killed eight people in San Bruno, Calif., released an interim report that ruled out outside corrosion and damage caused by a third party as the cause for the blast, but found that part of the pipe near the rupture was constructed with seam-welded pipe, which owner Pacific Gas & Electric reported as seamless.
The group, chaired by the NTSB, includes technical experts from the Pipeline and Hazardous Materials Safety Administration (PHMSA), the California Public Utilities Commission (CPUC), and PG&E.