In yet another wrinkle in Energy Transfer Partners LP’s (ETP) saga to expand its Mariner East (ME) pipeline system, Pennsylvania regulators on Wednesday petitioned for an emergency order to “immediately suspend” ME1 operations after three sinkholes were discovered near it.

The Pennsylvania Public Utility Commission’s (PUC) Bureau of Investigation and Enforcement (I&E) said the sinkholes in Chester County’s West Whiteland Township, which are likely linked to horizontal directional drilling operations for ME 2X, pose grave safety concerns for the public. ME 2X is a third pipeline that is under construction to parallel ME2, which is also being built.

ME 1 operations must be suspended I&E wrote in its petition to the full PUC “due to safety concerns regarding the integrity of said pipeline as being potentially hazardous to life, property and/or the environment.”

ME1 was commissioned in 2014 and went into full service about two years later. The 70,000 b/d pipeline moves ethane and propane from Western Pennsylvania to the Marcus Hook Industrial Complex near Philadelphia.

The sinkholes, I&E said, occurred at three locations within 550 feet along the path of the ME1 pipeline in an area where ETP subsidiary Sunoco Pipeline LP is constructing ME2 and ME 2X.

The first, eight feet wide and three feet deep, formed in December near Amtrak’s Keystone Line. A second sinkhole, eight feet wide and 15 feet deep, was discovered last week by Sunoco workers during ME 2X construction. A third sinkhole, the largest at 15 feet wide and 20 feet deep, was discovered last Saturday 10 feet from a house’s foundation. It had “partially exposed the buried ME1 pipeline,” according to I&E’s petition.

The first two sinkholes were located above ME 2X and near ME1. I&E claims in its petition that Sunoco did not notify the PUC, or the Pipeline and Hazardous Materials Safety Administration. The bureau did say that all three sinkholes were filled with specialty concrete on Saturday. But during an on-site inspection, I&E said that regulators discovered additional sinkholes forming in the area, where homes and apartments are located.

The I&E has asked the commission to suspend ME1 operations until repairs are satisfactorily completed. At that time, I&E said Sunoco could file a petition to reinstate transportation service.

The ME2 project in particular has so far had a rough path forward. The Pennsylvania Department of Environmental Protection, which issued the permits and is overseeing construction, fined Sunoco $12.6 million last month to resolve dozens of violations and allowed the project to restart construction.

Earlier this year, DEP suspended Sunoco’s permits and stopped nearly all construction activities in response to more than 30 separate violation notices and more than 100 inadvertent returns of drilling mud, fluids and other substances. It was not the first time that regulators ordered work to stop.

The 350-mile ME2 would transport ethane, butane and propane from processing facilities in Ohio, Pennsylvania and West Virginia to Marcus Hook. ME 2X would run parallel to it and deliver natural gas liquids as well.