At least 400 International Paper Co. employees, including contractors, were on site Saturday when the explosion tore through mill in Redwood, about 30 miles west of Jackson. One worker was killed and 17 others were injured, some critically.
The boiler had been shut down for annual maintenance before the blast.
"We're in the process of making sure the boiler is safe to access so we can begin to investigate the cause and assess the damage and repair needs," the company said in a statement. "We've met with employees and will continue to do so. Key priority is making sure employees who are working can do so safely and stay focused."
Marcus Christopher Broome, a 28-year-old contract worker, was killed, the Warren County coroner said.
Five people were transferred to a burn center in Augusta, Ga., while the others injured were treated at a nearby hospital and released, officials said.
Four burn victims were in critical condition and the fifth was in good condition on Sunday at the Joseph M. Still Burn Center, hospital spokeswoman Beth Frits said in a news release.
Officials from the federal Occupational Safety and Health Administration are investigating.
"This accident is the first of its kind in the mill's 40-year history, and our goal is to ensure it doesn't happen again," the company's statement said.
