ALBUQUERQUE, N.M. --

Four men are in the hospital after they were burned in a southwest Albuquerque neighborhood.

The Bernalillo County Fire Department said four men tried to start a grill at a family gathering near Wilshire Drive and Cerro Vista Street when a propane tank exploded at about 2 p.m. Sunday.

About 30 to 40 family members were outside sitting around the area when the explosion occurred. Neighbors said they could feel the explosion.

A small fire, that was put out immediately, started after the explosion.

Firefighters said they are not sure what caused the propane tank to explode, but said it was a commercial-sized tank about 5 feet tall. It was not the tank that fit the grill.

"My nephew was playing outside with my dog and we heard a big old popping sound. We came outside and I saw smoke and saw some guy against the pole with severe burns all the way down his arms," said neighbor Michael Benitez.

The victims suffered third degree burns to the chest, arms and face. There was no immediate word on their condition.

"Because they were burned in their face, their airways are involved so it could be life threatening. That's why we got them out of here so quickly," said BCFD Commander Marty Giron.

BCFD said it is investigating what caused the explosion. The state propane inspector and the fire marshal are also involved.

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