A pair of explosions and a fire, apparently sparked by leaking gas, ripped through a nursing home near Philadelphia, killing a female employee and a resident, and injuring 20 people, officials said.All residents and staff of the Silver Lake Nursing Home in Bristol Township, about 33km northeast of Philadelphia, have now been accounted for and the injured taken to local hospitals, police chief Charles Winik said.Winik said people had been feared missing for a number of hours as flames and blasts gutted the nursing home. Fire Marshal Kevin Dippolito said numerous patients and staff were initially trapped inside a demolished portion of the building.Dippolito said the first firefighters arriving on the scene, some from a fire-and-rescue station across the street, encountered "a major structural collapse," with part of the building's first floor crumbling into the basement below.He said numerous victims were extricated from debris, blocked stairwells and stuck elevators, while firefighters ventured into the collapsed basement zone and pulled at least two more people to safety before retreating amid lingering gas fumes."We got everyone out that we could, that we could find, that we could see, and we exited the building," Dippolito said. "Within approximately 15 to 30 seconds of us exiting the building, knowing there was a heavy odour of natural gas around us, there was another explosion and fire.”The front of the structure appeared to have been blasted away from the inside, but the majority of the facility remained standing, though most of its windows were shattered, according to a Reuters photographer on the scene.News footage from WPVI-TV, an ABC News affiliate, showed roaring flames and smoke billowing from the crippled building shortly after the first explosion.The precise number of patients and staff inside at the time was not immediately known. The nursing home is certified for up to 174 beds, according to an official Medicare provider site.More than 50 patients, ranging in age from 50 to 95, are typically in the building at any one time, WCAU-TV reported, citing a nurse employed by the facility who arrived on the scene after the blast. About five hours later, nursing home officials had informed authorities that all patients had been accounted for, Dippolito said.