Another sinkhole related to the embattled Mariner East 1 natural gas pipeline opened in the backyard of a West Whiteland Township home Sunday afternoon, authorities said, prompting safety concerns among residents.

The five-foot wide, 10-foot-deep sinkhole appeared less than a year after the Pennsylvania Public Utility Commission ordered pipeline operations to halt when sinkholes were found in the same neighborhood of single-family homes. The pipeline resumed operation last May.

On Sunday, a broken water-drainage system associated with Mariner East 1 caused the sinkhole behind a home on the 400 block of Lisa Drive, exposing a portion of the pipeline, the Chester County Department of Emergency Services said. Police were called around 4:30 p.m. The pipeline was voluntarily shut off.

No injuries were reported, no one was evacuated, public safety was not affected, and the pipeline was not damaged, the department said.

“We are working in coordination with the Pennsylvania PUC’s Bureau of Investigation and Enforcement and its consultants to perform activities to ensure the area remains stable," according to a statement from Energy Transfer LP, which manages the pipeline. "It is too early to know additional details at this time.”

The pipeline, which began operating in 1931 to funnel gasoline, was repurposed as a natural gas pipeline in 2014 by Sunoco Logistics, a subsidiary of Energy Transfer. Each day, the pipeline 8 inches in diameter facilitates the flow of up to 70,000 barrels of volatile natural gas liquids from the Marcellus Shale gas region in Western Pennsylvania to a Sunoco refinery in Marcus Hook. Mariner East 1 is part of a pipeline system that includes Mariner East 2 and Mariner East 2X.

Officials with Sunoco and the PUC responded to Lisa Drive on Sunday and Monday to evaluate the situation and “work together to come up with a game plan” to seal the hole with concrete, said Bill Turner, Chester County deputy director for emergency management. Several utility workers gathered on Lisa Drive on Monday to examine the sinkhole, with a bulldozer parked nearby.

Turner said Monday that he could not say exactly how the sinkhole appeared and directed questions to the PUC. Nils Hagen-Frederiksen, a spokesperson for the PUC, said he could not discuss specific details, citing an active investigation.

Locals said there was little mystery to the sinkhole.

“It’s riddled with caves of various sizes,” Eric Friedman, the spokesperson for Del-Chesco United for Pipeline Safety, said Monday of West Whiteland’s geologic makeup. “It’s unstable. The area has problems with roads sinking.... This is an area, frankly, that was recognized by citizens' groups as a geologically problematic area.... It seems like everyone knew this was going to be a problem except Sunoco and the PUC."

Del-Chesco United for Pipeline Safety, which calls itself a nonpartisan grassroots organization, said in a statement it wanted residents of Lisa Drive and nearby areas to be evacuated and moved out at least a half-mile from the pipeline, and for Gov. Tom Wolf to “immediately and permanently shut down both of these pipelines.”

In March 2018, Mariner East 1 was shut down by a PUC-issued emergency order when sinkholes appeared on Lisa Drive. The PUC lifted that emergency order two months later.

In December 2018, Chester County District Attorney Thomas Hogan announced that his office had opened a criminal investigation into the Mariner East pipeline, citing the sinkholes on Lisa Drive, contaminated water, and “not so subtle bullying” of local residents. He did not pinpoint any charges that Sunoco or its parent company could face.

Hogan’s announcement came amid a tumultuous year for Sunoco, which in February 2018 paid a $12.6 million penalty for violations that included drilling without permission related to Mariner East 2.

In May 2018, Pennsylvania’s Department of Environmental Protection said it had fined the company $355,622 for spilling drilling fluid while constructing Mariner East 2.

This month, Hogan said a pipeline worker had left in December an “obscene” series of comments on the Instagram page of a resident who posted concerns about the pipeline.

On Sunday, when the latest sinkhole emerged on Lisa Drive, Hogan said Sunoco hired constables who acted like a private security force and kept people at bay from the pipeline.

Back on Lisa Drive residents worry that the ground in their neighborhood is sinking.

“I feel really bad for the residents," said Christina DiGiulio, a former analytical chemist for the U.S. Department of Defense and an advocate for residents who live near the Mariner East pipeline project. “They’re up against Goliath.”

Construction on the Mariner East 2 pipeline was finished in late December 2018. The last leg of the pipeline, Mariner East 2X, is projected to be finished by late 2019.