Torrential rain and saturated ground likely caused an Energy Transfer Partners LP (ETP) pipeline in Western Pennsylvania to slip and explode on Monday, the company said, but the exact cause remained unclear as an investigation is underway.

Residents in Center Township, about 30 miles northwest of Pittsburgh, were jolted awake early Monday by what emergency management officials described as a massive explosion. ETP said the 24-inch diameter gathering segment of its Revolution system burst into flames at about 5 a.m. ET. The company’s monitoring system detected the blast and triggered valves that isolated the line. By 7 a.m., the fire had extinguished itself after the gas flow was cut off.

While there were no injuries, Center Township Police Chief Barry Kramer said the explosion toppled six high-tension towers, felling power lines and prompting authorities to shut a local road and part of a major highway. The incident initially knocked out power to 1,500 people in the region, but by Monday afternoon power had been restored and roads reopened. About 30 homes were evacuated, but by early afternoon most residents were allowed to return with the exception of those living on two streets near the blast.

One home and a garage a few hundred feet away from the pipeline were destroyed by the explosion in addition to multiple vehicles, authorities said.

The pipeline was placed into service last week and is part of the broader 100-mile Revolution system, which also includes 30-inch diameter pipeline, and has a capacity of more than 400 MMcf/d. The system gathers wet gas, beginning in Butler County, PA, passing through Center Township in Beaver County and into Washington County, PA. ETP inked a long-term deal with privately owned EdgeMarc Energy Holdings LLC in 2015, announcing at the time that it would build a cryogenic gas processing plant, fractionator and gathering lines to facilitate the agreement.

ETP spokeswoman Alexis Daniel said at the time of the blast, the company was in the process of purging and packing the gathering lines that feed the Revolution Plant in Washington County, where construction is complete.

Affiliate Rover Pipeline LLC also recently received authorization from the Federal Energy Regulatory Commission to begin operating its Burgettstown lateral, which is designed to gather supply from the Revolution Plant and another processing facility being developed by MarkWest Energy Partners LP in Washington County.

Energy analyst Genscape Inc. said it did not expect the explosion to significantly impact nominations on interstate pipelines. Columbia Gas Transmission LLC and National Fuel Gas Co. each have systems in the area, but Genscape said it had not seen revisions to meter nominations on those pipelines. The blast could, however, affect the Burgettstown lateral.

“There have not been any scheduled nominations on Burgettstown lateral previously,” Genscape said of the lateral, which entered service on Aug. 27. “If the explosion is contained to the Revolution pipeline, we do not expect any significant impacts to interstate operations in the area. However, this may hinder the ability of molecules to get onto Rover’s Burgettstown lateral going forward.”

The region has been inundated by rain since late last week. Kramer said ETP was flying personnel in from Dallas to conduct a root-cause analysis. The company stated “initial site assessment reveals evidence of earth movement in the vicinity of the pipeline.” Some roads throughout the hilly region were closed because of flooding, and parts of the state have declared county-wide disaster emergencies. Kramer said the pipeline that exploded is tucked into a valley near a residential area and a hill.

ETP stopped short of concluding that the incident was caused by a landslide. Kramer said the incident “needs more investigation to determine if that’s what contributed to or caused it. I don’t know at what point that occured. Was it after the event, before the event and did it cause the event?

“Fortunately, with all this rain we’ve had, I think it helped stop the spread of any kind of forest fire. It certainly would have burned at a much quicker rate,” Kramer said at a press conference earlier in the day. “It’s probably one of the largest fires I’ve seen.”

A local fire official at the press conference, whose home is about 10 miles away from the blast site, said he heard it. Photos and video from the scene showed a massive fireball. There was “intense heat as we got closer, a large fireball, and you could hear the escaping methane, like a jet plane,” the fire official said when asked to describe the scene.

The Pennsylvania Public Utility Commission (PUC) is overseeing the investigation, and spokesman Nils Hagen-Frederiksen confirmed that engineers from the pipeline safety division are on scene.

No environmental issues have been reported, Kramer said. Pennsylvania Department of Environmental Protection spokeswoman Lauren Fraley said PUC has primary jurisdiction over the intrastate system, but said the agency is “standing by to provide assistance and air monitoring if necessary once the site is safe to enter.”

Natural gas utility Peoples is conducting inspections of its mainlines and meters at each home in the area to ensure safety. Peoples spokesman Barry Kukovich noted that ETP’s system does not supply customers and said there have been no service interruptions.

Kramer added that while local authorities knew about construction on ETP’s gathering line, they did not know it had entered service. He said the county’s reverse 911 system was employed to notify residents. He also said multiple agencies from the region responded. The American Red Cross was also on the scene to assist.

ETP has established a hotline at (800) 445-5846 to field questions, complaints and take property claims from residents and local officials. The rain that has plagued the region is expected to move out on Monday, but flooding was still expected to remain an issue, authorities said.

The explosion is the latest to dog the region in what’s been an unusually wet summer across Appalachia. Leach XPress in West Virginia caught fire and exploded in June after what was later attributed by Columbia Gas Transmission LLC to a landslide.

It’s unclear when the remaining evacuees may be able to return to their homes and the school district had canceled classes.