Authorities in Bucks County, north of Philadelphia, said a gas leak may have led to the explosion, which caused part of the Silver Lake Nursing Home to collapse, leaving some people trapped in the fiery debris.

“At this time there are at least two fatalities. We know that there are some number of individuals still missing,” governor Josh Shapiro told a press conference.

The governor praised quick-thinking first responders, notably firefighters who “were quite literally climbing up ladders, handing individuals in this nursing home to police, who were at times carrying two people on their backs to safety.”

Bristol Township fire chief Kevin Dippolito said there was “a heavy odour of gas” when firefighters arrived.

When the explosion occurred, “there was a major structural collapse, with parts of the first floor falling into the basement, with persons trapped,” he said.

“They pulled many residents out of the building via windows and doors, stuck in stairwells, stuck in elevator shafts.”

Dippolito said five people remained unaccounted for, but that number was preliminary.

“We are still in rescue mode until we know the building is clear,” he said.

Shapiro said the facility had new owners as of this month, and that Pennsylvania health inspectors visited on Dec 10 and met with nursing home personnel to work out a plan to update the standards at the facility.