(Bloomberg) -- Federal regulators are investigating a major natural gas leak from an Equitrans Midstream Corp. gas storage facility in Pennsylvania that spewed more than 1 billion cubic feet of the climate-warming fuel into the atmosphere. 

The Pipeline and Hazardous Materials Safety Administration said it is probing the cause of the leak that persisted for 11 days at Equitrans’ Rager Mountain Storage facility in Jackson Township. 

Federal investigators are seeking to determine what went wrong and whether to take any enforcement action, PHMSA said in a statement. The agency, part of the Department of Transportation, has authority to issue fines or corrective orders that could delay a restart of the facility.

Equitrans said in statement it is coordinating with federal officials and the Pennsylvania Department of Environmental Protection. The company said it is conducting a study to quantify the gas loss and an investigation to determine the cause of the incident, as well as a complete environmental assessment at and around the facility. In addition, the company said it was conducting a comprehensive review of storage wells. 

In addition, the company said it began flowing gas out of the facility Dec. 1 after getting approvals from regulators following a five-day shut-in test that concluded Nov. 28 to estimate the amount of gas lost during the incident. 

The leak from a vent in an underground storage well was one of the most significant releases of methane, a potent global warming agent, in the US in the past several years. Equitrans’ preliminary and conservative estimate is that 100 million cubic feet of gas a day was released. That equates to a total of 15,800 to 20,300 metric tons of methane, according to BloombergNEF. 

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