Updated

Four children were airlifted to a Dallas hospital with critical burns after a gas can exploded on Christmas Eve next to an open fire pit in a backyard, a fire official said.

Two other children are in the hospital, one with serious injuries and the other with minor burns.

At least one of the children sprinkled gasoline on the fire Monday, and then left the can near the pit, said McKinney Fire Department spokeswoman Stacie Durham. The fumes from the can ignited, and all six children were nearby when it exploded, and the flames hit them, she said.

Deb Martin, a neighbor, told the Dallas Morning News she ran over to the house when she heard the explosion.

"It was a whoosh," Martin said. "I don't know how else to describe it, and the kids were screaming. I thought maybe it was a firecracker, but they kept screaming. Some of the kids were running from the backyard."

The injured children, ages 4 to 11, are related and some are siblings, Durham said. A fifth child also taken to the Dallas hospital was in serious condition, and a sixth was taken to a McKinney hospital with minor burns, she said.

The children were believed to have been left unsupervised in the backyard. Adults were inside the home at the time of the explosion.

There were several other children in the backyard that were unhurt, Martin said. She said she and other neighbors called 911 and removed the injured children's clothes because they were on fire.

A child who is believed not to have been injured ran into the home and told the adults there was an explosion and the children were on fire, Durham said.