An explosion tore through a paper mill Saturday after a boiler was inspected, killing a contract worker and injuring 17 others, the company said.

The explosion occurred as a boiler at the International Paper mill was being started after an annual maintenance shutdown in Redwood, about 30 miles west of Jackson, company spokeswoman Amy J. Sawyer said in a statement.

"We have accounted for all IP employees, and no employees were hurt. An investigation will be conducted to determine the cause of the accident," Sawyer said.

No details were available about the contractor who was killed, Warren County deputy coroner Kelda Bailess said.

The condition of the injured wasn't immediately known.

The company said no damage estimates were available.

"The recovery boiler area, its processes and equipment are the most rigorously documented and monitored of any in the mill," it said.

At least 400 employees, including contractors, were on site at the time of the blast, said John Adams, manager of environment health and safety. Officials from the federal Occupational Safety and Health Administration had arrived to investigate, he said.

"OSHA talked to one of the contract site managers. They took a look at the periphery of where the boiler is located because we can't get into the area proper because it's not safe yet," Adams said.

The blast loosened some siding in the recovery boiler building — one of six to eight structures at the plant — but the building was still standing, he said.

"We're still trying to get to the bottom of the details, and we have to secure the boiler. We have to make sure that the floors in the recovery boiler area are safe and that there won't be any exposure for the people in that area," Adams said.