Robert Olson, 20, was working near a storage tank filled with 40,000 gallons of corn mash when it exploded at Chippewa Valley Ethanol Co., authorities said.
The tank was thrown about 75 feet and landed on a tanker truck filled with ethanol, causing the fire.
Firefighters from 11 surrounding towns fought the blaze and pumped water on rail cars to keep them cool, Sheriff Kenneth Hanson said.
Troy Leonard was taken to a hospital with acid burns, according to a hospital spokesman. He was reported in fair condition.
Authorities did not know what caused the storage tank to explode. The blast occurred in the part of the plant where corn is turned into mash, which is later processed into ethanol.
About 40 people work at the plant, which also produces alcohol used for vodka and products such as hair spray and mouthwash. Olson was a contractor with Lundin Construction of Hanley Falls.
Gary Klemm, who works at a nearby plant, said he saw the explosion demolish the storage tank.
``I was coming down the road and I saw the top blow right off,'' Klemm said.
Benson is about 120 miles northwest of Minneapolis.
