WASHINGTON (AFP) – Eight people died Tuesday when fire swept through an abandoned building used by homeless people for shelter in New Orleans during an unusual cold snap, officials said.

Firefighters found the tin warehouse fully engulfed by flames and partially collapsed when they arrived at 2 am (8:00 GMT).

"There were two squatters (a man and a woman) on site who told firefighter they had narrowly escaped," said Gregory Davis, a spokesman for the New Orleans fire department.

"When the fire was extinguished they found eight other people that perished and two dogs."

The squatters said they had set alight trash in a large barrel to keep warm, Davis said.

Those who died were likely overcome by carbon monoxide as the building filled with smoke. A combination of the heat and gasses likely caused the fire to engulf the building, he added.

"What happens in some cases, the fire -- if the door's closed -- it can use up all the oxygen and if oxygen is introduced it'll react violently," he explained.

"In other cases once a room reaches an ignition temperature everything is going to ignite."

It took firefighters about 30 minutes to extinguish the blaze in the warehouse next to a rail yard.

The bodies have not yet been identified, Davis said.