AURORA, Minn. (AP) _ An explosion at a closed explosives plant killed three demolition crew workers and left a crater, 20 feet wide and a foot deep.

The cause of the blast Wednesday morning at the Viking Explosives & Supply Inc. plant had not yet been determined, but St. Louis County authorities said it might have been caused by chemicals stored there.

The victims, employees of J.J. Holmes Salvage, were identified as Ricky Craig Wirtz, 24, of Pengilly; Shane Matthew Lindula, 20, of Iron; and David Karl Jones, 24, of Hibbing.

The victims were found outside a building where explosives used to be kept. They were believed to have been working outside the building at the time of the blast, said Lt. Randy Lehman of the St. Louis County sheriff's department.

The explosion also caused extensive damage to two smaller buildings, and blackened everything within about 100 square yards.

The the blast could be felt as far as 20 miles away.