Editor’s note: A statement sent in after the story was published by Food & Water Action Pennsylvania Director Sam Bernhard has been added to it.

HARRISBURG — The FBI has begun a corruption investigation into how Gov. Tom Wolf’s administration came to issue permits for construction on a multibillion-dollar pipeline project to carry highly volatile natural gas liquids across Pennsylvania, The Associated Press has learned.

FBI agents have interviewed current or former state employees in recent weeks about the Mariner East project and the construction permits, according to three people who have direct knowledge of the agents’ line of questioning.

All three spoke on condition of anonymity because they said they could not speak publicly about the investigation.

The focus of the agents’ questions involves the permitting of the pipeline, whether Wolf and his administration forced environmental protection staff to approve construction permits and whether Wolf or his administration received anything in return, those people say.

The Mariner East pipelines are owned by Texas-based Energy Transfer LP, a multibillion-dollar firm that owns sprawling interests in oil and gas pipelines and storage and processing facilities. At a price tag of nearly $3 billion, it is one of the largest construction projects, if not the largest, in Pennsylvania history.

However, the construction has spurred millions of dollars in fines, several temporary shutdown orders, lawsuits, protests and investigations. When construction permits were approved in 2017, environmental advocacy groups accused Wolf’s administration of pushing through incomplete permits that violated the law.

Wolf’s administration declined comment on the investigation Tuesday. In the past, Wolf and his administration have said the permits contained strong environmental protections and that the Department of Environmental Protection wasn’t forced to issue the permits.

An Energy Transfer spokeswoman said the company had not been contacted by the FBI about the Mariner East.

The chief federal prosecutor in Harrisburg, U.S. Attorney David Freed, declined comment.

The Mariner East project, along with the overhaul of the Marcus Hook refinery and export terminal near Philadelphia, have had the support of leading public officials and business trade groups.

Wolf himself has said that the pipeline’s economic benefits would outweigh the potential environmental harm, and that the Mariner East would be part of a distribution system that the industry needed.

The state’s building trades unions have seen a huge influx of work on the Mariner East pipelines and Marcus Hook. Exploration firms drilling in the booming Marcellus Shale and Utica Shale fields shipping natural gas liquids through Mariner East pipelines and Marcus Hook have helped the U.S. become the world’s leading ethane exporter.

The roughly 300-mile Mariner East 1 was originally built in the 1930s to transport gasoline westward from Marcus Hook. It was renovated and, in 2014, began carrying natural gas liquids eastward to the refinery from southwestern Pennsylvania’s drilling fields.

Construction permit applications were submitted in 2015 for two wider pipelines, the 350-mile-long Mariner East 2 and 2x, designed for the same purpose, but stretching farther, through West Virginia’s northern panhandle and into Ohio.

Both were projected to be open in 2017. But Mariner East 2 began operating in late December, and Mariner East 2X could be complete in 2020.

The pipelines run past houses, parks and schools in southeastern Pennsylvania, and have been met with protests by alarmed neighbors worried that one leak could ignite a deadly explosion. Sinkholes along the pipelines’ route have opened on lawns and construction has contaminated streams and private water wells.

Food & Water Action Pennsylvania Director Sam Bernhardt released the following statement after the story was published.

“Whether it is provided by the federal judicial system, county District Attorneys, or Governor Wolf himself, justice for communities harmed by Energy Transfer and their Mariner East pipeline means shutting this pipeline down for good.," he wrote. "The Wolf administration fast-tracked this dangerous, disastrous project, putting communities across the Commonwealth at risk. We have seen sinkholes, spills and water contamination, and a grassroots opposition movement has pushed his administration to stop the project before further disasters strike. Governor Wolf has refused.”

Meanwhile, county and state prosecutors are investigating the pipeline.

Chester County’s district attorney, Tom Hogan, opened an investigation last December. In March, Pennsylvania’s attorney general, Josh Shapiro, said his office had opened an investigation on a referral from Delaware County’s district attorney. His office already had an environmental crimes investigation under way into the natural gas industry.

Wolf’s administration also has had run-ins with Energy Transfer in which it accused the company of willfully violating state law.

Still, when the Department of Environmental Protection issued the permits, environmental advocacy groups warned that it would unleash massive and irreparable damage to Pennsylvania’s environment and residents. In general, the permits are required to protect waterways and wetlands from pollution, runoff and obstruction stemming from heavy construction.

Within hours, the Clean Air Council and other environmental advocacy organizations appealed the permits, saying the DEP had approved incomplete and inaccurate permit applications that violated the law “in response to heavy and sustained political pressure.”

At the time, Wolf denied applying pressure to approve the pipeline permits. Rather, he said he had simply insisted the department stick to its own timeline to consider them and that he believed the department had done its due diligence.

The environmental groups’ request to halt construction was denied, but they did win additional protective steps in a settlement.

In depositions and internal documents that became exhibits in the appeal, department employees said the schedule to consider the applications had been sped up, but none said they had been forced to approve permits over their objections.