Experts say a weld or weak section may have caused catastrophic failure of the 54-year-old natural gas pipeline that exploded in flames three weeks ago in San Bruno.

The National Transportation Safety Board this week allowed photographers to take pictures of the segments of pipe in the devastated neighborhood where eight people died and dozens of homes were destroyed.

Experts asked by the San Jose Mercury News to analyze the photos say the failure may have started along a weld or in a weakened section.

Stanford University mechanical engineering department chairman Tom Bowman says the pipe "unpeeled and failed catastrophically."

The experts suggested brittle pipes, old welds, corrosion or widening cracks could have caused the failure.


Information from: San Jose Mercury News, http://www.sjmercury.com