The Chester County District Attorney’s Office in southeast Pennsylvania said Wednesday it has opened a criminal investigation into the construction of the Mariner East (ME) 1, 2 and 2X projects.

District Attorney Tom Hogan said the investigation would include project owners Energy Transfer LP, affiliate Sunoco Pipeline LP and other related entities. The companies’ corporate officers and even project workers may face potential charges including criminal mischief and environmental crimes, among others. The companies have been notified of the investigation, Hogan said.

“In the last two years, we have seen these pipelines rip through the heart of Chester County. We have seen sinkholes created by the pipeline drilling, contaminated well water, and some subtle and not-so-subtle bullying of Chester County citizens by big corporate interests,” Hogan said. “We expected the state regulators and the governor to step in and assure the safety of Pennsylvanians.” Hogan said his office will “demand that every aspect of these pipelines be conducted safely, or we will bring into play all of the tools of the criminal justice system.”

Energy Transfer spokeswoman Lisa Dillinger said the company was caught off guard when it learned of the investigation. “We vehemently deny any such wrongdoing, and we take issue with the many factual inaccuracies” included in the district attorney’s announcement.

“We are confident that we have not acted to violate any criminal laws in the commonwealth of Pennsylvania, and we are committed to aggressively defending ourselves against these baseless allegations.”

ME 1, an old refined products pipeline built in the 1930s, was converted in 2013 to move 70,000 b/d of ethane and propane. It’s currently operational, while ME 2 and 2X are under construction. The pipelines bisect Chester County in heavily populated areas that have faced repeated issues during construction.

As a result, the ME projects have faced intense regulatory scrutiny, which has prompted the company to work more closely with state officials and inspectors, Dillinger said. The project was suspected, but never directly tied to water contamination in Chester County last year, sinkholes also formed near pipeline construction in the county earlier this year and the state Department of Environmental Protection imposed a historic $12.6 million fine last February to resolve dozens of violations during construction.

Work stoppages and temporary suspensions of service on ME 1 imposed by state regulators have plagued the project. Most recently, the state Public Utility Commission’s (PUC) Bureau of Investigation and Enforcement raised concerns about corrosion controls along the entirety of ME 1 — which runs from western Pennsylvania to eastern Pennsylvania — following an extensive investigation that started after a small leak on the system last year.

ME 2, now expected to enter partial service by the end of the year, was originally scheduled to start-up in 2016. ME 2X is now slated to begin service next year.

Hogan said staff conducted legal research to make sure the office has jurisdiction to pursue charges. The investigation is expected to be a lengthy process.

“This investigation will not be easy,” he said. “It will take time to dig into the historical information and we will need to constantly monitor any future activity. But we are committed to protecting Chester County. And we will need our citizens to help.”

Dillinger said the company hopes to open “a dialogue” with Hogan’s office “in the hope that we can bring this matter to an appropriate resolution.” She said safety remains a top priority as the projects near completion.

Formal complaints filed against the project by a state lawmaker and residents from the region are already pending before the PUC.

ME 2 and 2X would run parallel for about 350 miles alongside part of ME 1 to move ethane, butane and propane from processing facilities in Ohio, Pennsylvania and West Virginia to the Marcus Hook Industrial Complex near Philadelphia.