A thunderous explosion at a nursing home just outside Philadelphia collapsed part of the building and left people injured and possibly trapped inside, authorities said.

The explosion happened at Bristol Health & Rehab Center in Bristol Township, just as a utility crew had been inside looking for a gas leak, although the cause of the explosion was unclear several hours later, as were the extent of the casualties.

A plume of black smoke rose from the nursing home, as emergency responders, fire trucks and ambulances from across the region rushed there, joined by earthmoving equipment.

Authorities said there were injuries, but had yet to say whether there were any fatalities.

Police Lt. Sean Cosgrove said he didn't know if anyone was missing, and that residents had been evacuated by emergency responders, bystanders and staff.

“A lot of the details at this point are still unknown,” he told reporters at the scene.

Bucks County emergency management officials said they received the report of an explosion at approximately 2:17 p.m. and said a portion of the building was reported to have collapsed. Ruth Miller, a Pennsylvania Emergency Management Agency spokesperson, said her agency had been informed that people were trapped inside.

Willie Tye, who lives about a block away, said he was sitting at home watching a basketball game on TV when he heard a “loud kaboom.”

“I thought an airplane or something came and fell on my house," Tye said.

He got up to go look and saw “fire everywhere” and people escaping the building. The explosion looked like it happened in the kitchen area of the nursing home, he said. Tye said some of the people who live or work there didn't make it out.

“Just got to keep praying for them,” Tye said.

The cause of the explosion was unclear.

The local gas utility, PECO, said its crews had responded to reports of a gas odor at the nursing home shortly after 2 p.m.

“While crews were on site, an explosion occurred at the facility. PECO crews shut off natural gas and electric service to the facility to ensure the safety of first responders and local residents,” the utility said in a statement.

Nils Hagen-Frederiksen, press secretary at the Pennsylvania Public Utility Commission, said investigators from the safety division were headed to the scene.

Hagen-Frederiksen said first responders and emergency management officials were describing it as a gas explosion, but that won’t be confirmed until his agency can examine the scene up close.

Musuline Watson, who said she was a certified nursing assistant the facility, told WPVI-TV/ABC 6 that, over the weekend, she and others there smelled gas, but “there was no heat in the room, so we didn’t take it to be anything.”

The nursing home is about 20 miles (32 kilometers) northeast of Philadelphia. Its owner, Saber Healthcare Group, said it was working with local emergency authorities. The facility had been known until recently as Silver Lake Healthcare Center.

Jim Morgan, president of the Bristol Township School Board, said district buses would take people from the nursing home to a reunification center at Truman High School. He said officials were working on setting up beds and providing water and other needs to residents.

“This is just something that is sad for everybody and the families and the workers that are there,” Davis said.

According to Medicare.gov, the 174-bed facility underwent a standard fire safety inspection in September 2024, during which no citations were issued. But Medicare’s overall rating of the facility is listed as “much below average,” with poor ratings for health inspections in particular.