Sunday, June 17, 2007 The National Transportation Safety Board (NTSB), the agency responsible for investigating transportation accidents in the United States, released updates on three major investigations on June 14. The NTSB, well known publicly for its involvement in the investigation of aviation incidents which involve harm or loss of human life, is also an agency that oversees the transportation of refined petroleum and gas products, chemicals and minerals. The agency determined the cause of a natural gas pipeline explosion that killed six. It also detailed the cause of an accidental release of 204,000 gallons of anhydrous ammonia from a pipeline in an environmentally sensitive area, and released preliminary information…