BAYVIEW, Idaho -

A boat exploded and caught fire at Bayview marina on Lake Pend Oreille, burning an Idaho Falls man and his grandson.

Timberlake Fire Protection District Chief Kevin Kleinworth says 70-year-old Richard Wagner and his 8-year-old grandson suffered severe burns and were forced to jump into the lake Tuesday afternoon to escape the fire.

Witnesses say the boat exploded when it was started. The Kootenai County sheriff's office says the fire was probably caused by fuel vapors that built up in the engine's bilge and were not properly evacuated before the boat was started.

Kleinworth says bystanders prevented a lot more fire damage by pushing the burning boat away from the dock. A marina employee suffered minor burns on his arms while pushing the boat away with a pole.