Federal regulators late on Friday were preparing to take over the investigation of a massive explosion and fire on a portion of a Texas Eastern Transmission mainline in Westmoreland County, PA, that left one person severely burned and caused significant property damage in the area.

Pennsylvania Department of Environmental Protection (DEP) spokesman John Poister said the system’s 36-inch mainline ruptured, exploded and caught fire at 8:30 a.m. EDT on Friday. The fire had been extinguished by early afternoon, but first responders, utility workers, state regulators, area residents and others were left to deal with the aftermath.

Spectra Energy Corp. personnel on Friday afternoon were conducting a controlled release of some of the natural gas that’s still built up in the system. DEP said it’s a looped line with four pipelines running parallel to one another in the right-of-way, adding that it’s unclear which of the pipelines caused the incident and how badly damaged each one is.

Texas Eastern (Tetco) declared a force majeure and an operational flow order downstream for its Delmont Compressor Station on its Penn Jersey LIne, dropping nominations to zero/dthat about 11 a.m. on Friday. It also issued a number of operational flow restrictions and imbalance warnings on its system, noting that excess takes beyond limited amounts could lower line pack, further hindering deliveries. Tetco continued adjusting and issuing system orders throughout Friday, the latest at 3:14 pm. Because the status of the pipes and repair is still unclear the orders carried a nominal end date of June 1.

The explosion and fire completely destroyed a home in the area and damaged several others, Poister said. Trees and utility poles were also toppled by the blast. FirstEnergy Corp. subsidiary West Penn Power was working to restore electricity service to about 500 customers in the area.

One resident in a nearby home was injured with severe burns and transported to a Pittsburgh hospital. It’s unclear what caused the blast, which occurred off Route 819 in Salem Township, about 30 miles east of Pittsburgh. The U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration was set to take over the investigation on Friday afternoon, DEP said.

“If they’re not already on the scene, they will be shortly,” Poister said. Homes and businesses within a quarter mile of the fire were evacuated, he added, saying the order would remain in effect until further notice as a precaution.

“Our first concern is for the safety of the community, our employees and any others who may be affected,” Spectra said in a statement early Friday. “We have activated our emergency response plan. We are cooperating with authorities in our response, and we will provide more information at a later time.”

Videos posted by local residents and footage from news media at the scene showed the fire blazing hundreds of feet into the air. Buildings can also be seen very close to the blast. Poister said it “was a pretty intense fire and explosion.” He added that crews were able to shut off the flow of gas feeding the fire and bring it under control.

Complicating matters, a nearby natural gas injection well operated by Dominion has been shut-in. Officials plan to conduct a mechanical integrity assessment prior to placing it back in service.

The disaster is likely the worst in the region involving a pipeline since 2012, when the Columbia Gas Transmission system ruptured in Sissonville, WV, causing significant damage to several residences and Interstate 77 (see Shale Daily, Dec. 13, 2012).

Friday’s incident had already attracted the criticism of local groups that are opposed to oil and gas development in the state. The Sierra Club’s Pennsylvania Chapter issued a statement about the incident by midday.

“Today’s explosion is a tragic reminder of the dangers dirty fuels pose to our communities,” Director Joanne Kilgour said. “…We urge state and federal agencies to conduct a thorough investigation and hold Spectra accountable for today’s disaster and bar it from reopening this pipeline until a full review is conducted.”

With 9,096 miles of pipeline, Texas Eastern is a vital piece of infrastructure that connects the Gulf Coast with high-demand markets in the Northeast. The pipeline can transport up to 10.46 Bcf/d.