Officials said Wednesday they located everyone after hours of searching.

Bristol Township’s police chief said he had “never seen such heroism,” and a speech therapist working there described feeling the building shake during Tuesday’s explosion and hastily getting a bedridden resident out, bed and all.

“They were rushing towards a building where, at a distance of 15 meters, I could still smell gas and walls that seemed about to collapse,” Police Chief Charles Winik told reporters Wednesday.

Responders spent hours searching the badly damaged building and checking with hospitals overnight Tuesday to locate the missing. But officials said they did not yet know the cause of the explosion, although a utility crew was on scene investigating a reported gas leak.

The explosion sent 20 other people to hospitals, including one person in critical condition. The rest of the 120 residents were transferred to nearby nursing homes, authorities said.

The Bucks County Coroner’s Office said the employee who died was 52-year-old Muthoni Nduthu. Authorities did not immediately identify the resident who died at a Philadelphia hospital. Both victims were women.

Nduthu’s sister said she was a great mother to her sons, a wonderful wife, a devout Catholic and very involved in the community. A Kenyan immigrant, she studied nursing, loved cooking and worked hard, said her sister, Rose Muema.

“She was an immigrant who came to make a difference in this country, and she did,” Muema said.

Nineteen people were still hospitalized Wednesday, Winik said.

The explosion was so powerful that it shook neighboring homes for several blocks in Bristol, about 20 miles (32 kilometers) northeast of Philadelphia.

A wing of the facility including the kitchen and cafeteria was almost completely destroyed, leaving the roof collapsed, sections of walls completely missing and windows from adjacent walls torn out. Debris littered the ground.

Winik said the scale of the casualties could have been much worse. Police and firefighters streamed from the area, while staff from a nearby hospital, nursing home workers and neighbors rushed to help evacuate people. One person was resuscitated at a hospital, authorities said.

They found people trapped on stairs and elevator shafts and under rubble, authorities said. Some residents could not walk and some were in wheelchairs or bedridden. A second explosion occurred while rescue work was underway.

Speech therapist Julia Szewczyk described the experience as terrifying and devastating.

She was in a group therapy session in another part of the building when it started shaking. She and other staff members rushed to evacuate residents across a street to safety.

“And then the next thing was to go in and catch more people,” Szewczyk, 25, said.

They dragged a bedridden resident out into the cold, then Szewczyk twice ran into the burning building to retrieve blankets from a supply closet. A co-worker got stuck in an elevator during a power outage, she said.

Outside during the rescue, employees were looking for Nduthu, Szewczyk recalled.

Federal agencies were prepared to help with the investigation, but the collapsed walls and roof had to be cleared first, Winik said.

A utility crew was responding to reports of the smell of gas when the explosion occurred, authorities said. The local gas utility, PECO, said the crew shut off natural gas and electric service to the facility, but did not know whether utility equipment or gas was involved in the explosion.

Musuline Watson, who said she was a certified nursing assistant at the facility, told WPVI-TV that staff smelled gas over the weekend, but did not initially suspect a serious problem because there was no heat in that room. Other employees told Szewczyk they smelled gas earlier in the day Tuesday, Szewczyk said.

The nursing home recently affiliated with Ohio-based Saber Healthcare Group, which called the explosion “devastating” and said in a statement that staff at the facility quickly reported the gas smell to the local gas utility before the explosion.

Willie Tye, who lives about a block away, said he was watching a basketball game when he heard a loud boom.

“I thought a plane or something had come and fallen on my house,” he said.

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Levy and Scolforo reported from Harrisburg, Pennsylvania. Associated Press journalists Mingson Lau in Bristol, Pennsylvania; Holly Ramer in Concord, New Hampshire and Michael Casey in Boston contributed to this report.