Federal officials are investigating how a methane gas pipeline exploded in West Reading, Pennsylvania, last Friday, killing seven and sending 10 more to the hospital, the National Transportation Safety Board announced Tuesday. While the exact cause of the explosion is still under investigation, “Initial findings by the NTSB investigator who had been at the site indicates an accident involving a natural gas pipeline … causing the explosion at the Palmer factory,” a statement from an NTSB spokesperson said. Gas pipeline explosions and other incidents are not uncommon. A major leak from a gas pipeline is reported to federal regulators more than every other day. (AP, CBS; NTSB statement: WGAL)