One person was killed Monday and at least five others were injured in an explosion that caused a large fire at Verso Paper Corp., a mill in Sartell, Minn.

The name of the person killed was not immediately released, nor were the names or conditions of those injured when an air compressor apparently exploded at the plant shortly before 11:30 a.m.

Three of the injured were treated at St. Cloud Hospital and released, Sartell City Manager Patti Gartland said Monday.

The mill recently celebrated its 100th anniversary, Gartland said. She said the mill employs about 260 people and is the second-largest employer in the town, which has a population of about 16,000. About 50 people were working at the time of the blast, plant manager Matt Archambeau said. Gartland said the person killed was an employee.

"The paper mill is part of the heart and soul of the community," Gartland said. "I think it's kind of sinking in."

The city of Sartell plans to bring in a structural engineer to check the integrity of the paper mill as it begins investigating exactly what led to the explosion.

Chris Havens — St. Cloud Times, Star Tribune
An explosion and fire broke out Monday, May 28, 2012, at the Verso Paper mill in Sartell.

At least one firefighter was treated for heat exhaustion, according to Gartland. At least 15 fire departments responded to the blaze, which was about 90 percent under control by evening, she said.

"We called everybody out," she said. "There was a lot of debris flying around."

Could burn for another day

Gartland said the fire could burn for another day or so because of large paper bales inside the warehouse area of the plant. She said the roof collapsed on top of the bales, which weigh tons, and that is hindering efforts to extinguish the fire.

The American Red Cross provided food and water for about 230 firefighters, as well as some mill employees, the agency said Sunday afternoon.

Blast damaged sprinklers

Authorities said no hazardous materials appeared to have been exposed to the fire, but they were warning nearby residents to stay indoors and close windows because of the smoke.

The building's sprinkler system was damaged in the explosion, Gartland said.

As a result, she said, water had to be brought in to fight the fire.

Matt Dahl, who lives nearby, said the explosion was large enough to shake his house. He said he ran outside to see flames and smoke shooting from the mill.

-- The Associated Press contributed to this report.

Chris Havens • 612-673-4148 Heron Marquez • 952-746-3281