An 8-year-old boy was in critical condition in the Intermountain Burn Unit at University Hospital Friday after a small fire he started with some friends exploded.

Alex Jensen suffered burns to at least 80 percent of his body, Salt Lake County Fire Capt. Bill Brass said.Jensen and two other boys, Lavery Bow, 9, and Casey Beach, 11, lit a fire on a log while playing inside a hut they had built with decorative cinder blocks behind Jen-sen's home, 13727 S. Rocky Point Drive (5405 West), just before 2 p.m. Friday.

Apparently, a quart jar of gas sitting on the floor of the 5-by-3-foot structure was knocked over and spilled into the fire, causing a small explosion. Jensen's clothes ignited because he was closer to the fire than the other boys, Brass said.

All three boys escaped from the hut. Jensen dropped to the ground and rolled in dirt to put out the flames and then ran to a neighbor's house, where they doused him with water.

He was transported by helicopter to the hospital. Paramedics at the scene said he suffered second- and third-degree burns, Brass said.

Bow and Beach were transported by ambulance to Jordan Valley Hospital where they were treated and released.