At least three people were killed and five injured after an explosion ripped through a three-storey apartment building in New Jersey.
Bitterly cold temperatures and snow have hit New Jersey this week
Police said a further four people were still unaccounted for by late Tuesday.
A cloud of smoke visible from neighbouring Manhattan billowed from the building in Bergenfield following the morning blast.
Neighbours were removed as emergency services rushed to the scene, several miles north-west of New York City.
Initial reports suggested that a gas leak may have caused the explosion at around 0930 (1430 GMT).
Local sheriff Leo McGuire told US TV networks the fire may have been started by a contractor working near high-pressure gas lines.
"Thirty families are going to be homeless throughout the holiday period," he added.
Television pictures showed a plume of steam and smoke rising from the building.
Firefighters used hoses and cannons to blast the building with water and retardant.
The BBC's Jeremy Cooke in New York says that bitterly cold weather has forced many to turn their domestic heating on continually to keep warm.