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FIRESTONE, Colo. — A two-and-a-half year investigation by the National Transportation Safety Board found a 2017 house explosion in Firestone was caused by a leak in an improperly abandoned pipeline that was most likely severed during the construction of the house.

According to the investigative files released by the NTSB, the federal agency tasked with investigating pipeline accidents in the US, “local authorities” also contributed to the accident by allowing homes to be built next to oil and gas production fields without having complete documentation from the operator about the location of all the pipelines it owned.

Although the investigation found no records showing when the line was cut, NTSB investigators found the only known construction at the residence occurred in 2015, when the house was being constructed.

The investigation also determined there were three severed lines about six feet from the foundation of the house that were all initially connected to natural gas lines.

The explosion obliterated the home and killed Joey Irwin and his brother-in-law, Mark Martinez. They were installing a water heater when the blast happened.  Irwin’s sister, Erin, who was also Martinez’s wife, was burned in the explosion.

A spokesperson for the Colorado Oil and Gas Conservation Commission, which regulates oil and gas development in Colorado, said all oil and gas companies in the state have until Oct. 31, 2019 to deliver maps of their underground pipelines and flowlines to the state. The agency has plans to make that map public in the near future.

Meanwhile, COGCC has also posted draft rules that will add safety measures to flowline regulations. It expects to adopt final rules sometime in November.

The agency also said it will now proceed with an enforcement action against the oil and gas company involved with the explosion by issuing a Notice of Alleged Violation (NOAV).

“We respect and appreciate the National Transportation Safety Board’s (NTSB) review of this tragic accident, along with all of the local agencies engaged throughout this process. We take the findings very seriously, and as part of our commitment to safety, we continually review our processes and procedures,” said Jennifer Brice, a spokesperson for Occidental, the company that acquired the oil and gas company that owned the infrastructure in question.

“Many of the steps taken following this tragic accident are outlined on our Colorado Response Page. We are mindful of the events of April 17, 2017, every day, and our thoughts continue to be with the families, friends and communities affected by this tragedy,” she said.