The huge fireball was captured from a house across the road in the borough of Plum in western Pennsylvania.

In the video, the quiet residential street containing carefully mown lawns is suddenly filled with heat and debris.

One house was reduced to rubble while two others were engulfed in flames.

The bodies of four adults and a young person were recovered following the blast shortly before 10.30am local time on Saturday, Plum Borough Police Chief Lanny Conley said.

Three people were taken to hospital, one of whom was in a critical condition. The other two were discharged, local emergency services said.

Crews from at least 18 fire departments tackled the flames with the help of water tankers from Allegheny and Westmoreland counties.

Gas and electric services were closed off as a precaution.

The county fire marshal's office is investigating the cause of the explosion along with borough and county police.

It will be a "slow and long process" including a lot of forensic testing and could last "months if not years", said Steve Imbarlina, deputy director of fire and emergency services for Allegheny County.