NOME, Alaska (AP) _ A 14-year-old boy was in critical condition today with burns suffered when an empty, icebound petroleum barge exploded, killing two other children and breaking windows in nearby houses, officials said.

Mike Walker was burned over about 90 percent of his body in the blast Sunday, said Larry Lancaster, a nursing supervisor at Harborview Medical Center in Seattle, where the youth was flown for treatment.

Police identified the children killed as Steve Cunningham, 12, and Frank Butler, 14.

Children had been chased off the barge during the past three days, said Don Stultz of the Arctic Lighterage Co.

The cause of the explosion was not immediately determined, said Fire Chief Angelo Buffas.

The vessel was one of several barges that have been frozen in pack ice in Nome's harbor since last fall. The barges are used to carry petroleum products and are flushed out with diesel fuel in the fall, according to Stultz.

The blast blew off the deck of the barge. Damage was estimated at $500,000.

It took 30 firefighters to put out the fire, Buffas said.