More than 48 hours after the deadly explosion in Oak Cliff, federal investigators and Atmos crews remained on site. The National Transportation Safety Board (NTSB) sent a team of eight investigators to Dallas. The NTSB said its investigation will focus on three areas: human factors, the pipeline system and the operating environment. Geoff Henley, an attorney representing the owner of the Clyde apartments, told NBC 5 the property was in escrow and the buyer had hired an engineering firm for soil testing. According to Henley, a subcontractor was boring in the area on Thursday when the gas line was hit and the ruptured line ignited. Henley identified the subcontractor as Addison-based Barba Drilling. NBC 5’s calls and messages to Barba Drilling went unanswered on Saturday. “My client and the management team they all mourn the loss of these folks,” said Henley. “They are absolutely stunned and shocked by all of this.” Henley said his clients have cooperated with investigators and have been trying to find housing for tenants. “We’ve heard some anecdotal evidence as to what might have happened, but everybody will say this, you have to wait until the investigation goes through,” said Brigham McCown, Senior Fellow and Director, Initiative on American Energy Security, Hudson Institute. McCown is a former head of the federal government’s Pipeline and Hazardous Safety Materials Administration which oversees the nation’s 3.3 million miles of pipeline. “The number one cause of pipeline accidents aren’t the pipeline themselves, nearly two-thirds of all pipeline accidents come from excavation damage, meaning somebody is digging where they shouldn’t be digging,” McCown said. He helped roll out the ‘811 Call Before You Dig’ program and says it will play a critical role in this investigation. “We don’t know if 811 was called. We don’t know if they showed up and marked the lines, didn’t mark the lines,” McCown said. “Were the lines actually even properly marked? Were they digging with hand tools in close proximity to what was marked? All these questions will come out during the investigation.” McCown said once investigators have answers, they’ll make recommendations to prevent future tragedies. “We want to find out what happened and make sure that it’s preventable and doesn’t occur again,” said McCown ...read more read less