Two people have died and 20 others have been injured after two explosions and fire at a Pennsylvania nursing home caused a partial collapse of the building.

Emergency crews were called to the Silver Lake Nursing Home in Bristol at about 14:00 local time on Tuesday after receiving reports of an initial explosion and an odour of gas, said fire chief Kevin Dippolito.

Crews evacuated people from the building, and just 15 to 30 seconds after they left, a second explosion followed, resulting in a fire, Mr Dippolito added.

Authorities have suggested the cause could be a gas leak, though investigations are ongoing.

In a statement, local gas firm PECO indicated that the explosion occurred while its crews responded to reports of a gas smell. They noted it's still unclear whether their gas or equipment was involved in the incident.

Images shared on social platforms reveal a partially collapsed building with massive flames emanating from it.

Describing the rescue efforts post-explosion, Mr Dippolito recalled one police officer who heroically carried two individuals to safety. Several others were trapped in the basement but were ultimately rescued.

Five individuals who were unaccounted for after the blasts have since been located, affirmed police chief Charles Winik.

Witnesses recounted hearing a thunderous explosion. One nearby resident described it as a loud ka-boom, initially fearing an aircraft had crashed into his home.

Family members of nursing home residents expressed their anxiety as they awaited news. Cathleen O'Donnell, anxiously seeking updates on her sister, Sandra Hart, shared her relief upon learning her sister was alive, though she awaited further news on her condition.

Pennsylvania Governor Josh Shapiro commended the efforts of local authorities and surrounding residents, stating, We had residents coming out of their houses offering to help us. This is the Pennsylvania way: neighbours helping neighbours in a moment of need.