One of three friends fixing up a junked pickup truck to use in a demolition derby died after a capped pipe he was trying to cut exploded in a blast of shrapnel, authorities said.

Investigators were trying to determine Monday whether the pipe might have been a discarded bomb left in the junked pickup.

Polk County Sheriff Tim Moore said a metal-cutting saw set off the blast.

"The friction from the saw was like lighting a fuse," Moore said. "It was a fierce blast — a horrific explosion. I've never seen anything like it in 25 years."

Charles Juleff, 21, of Clayton, was using the saw and died from massive trauma, authorities said.

The explosion, which happened about 7 p.m. Saturday, peeled back a metal plate of the trailer used to haul the pickup. Shards of metal went flying through a nearby trailer home.

The sheriff said officials located the truck's original owner, who told authorities he knew nothing about the pipe and had junked the vehicle about five to eight years ago.

Investigators with the Polk County sheriff's office, state Division of Criminal Investigation and federal Bureau of Alcohol, Tobacco and Firearms searched the grounds around the blast Sunday, recovering metal fragments.