inputs: hypothesis: NTSB is responsible for investigating transportation accidents in the United States. premise: In the gas explosion disaster, the towing vessel Miss Megan, which was of specifications that did not require inspection by the United States Coast Guard, was being operated in the West Cote Blanche Bay oil field in Louisiana by Central Boat Rentals on behalf of Athena Construction on October 12, 2006. The Miss Megan was pushing barge IBR 234, which was tied along the starboard side of barge Athena 106, en route to a pile-driving location. Athena Construction did not require its crews to pin mooring spuds (vertical steel shafts extending through wells in the bottom of the boat and used for mooring) securely in place on its barges and consequently this had not been done. During the journey, the aft spud on the Athena 106 released from its fully raised position. The spud dropped into the water and struck a submerged, high-pressure natural gas pipeline. The resulting gas released ignited and created a fireball that engulfed the towing vessel and both barges. The master of the towing vessel and four barge workers were killed. The Miss Megan deckhand and one barge worker survived. One barge worker is officially listed as missing.