CANTONMENT, Florida (From the Pensacola News Journal) -- An extended shutdown at International Paper's Cantonment mill allowed a gas buildup that caused the facility's Jan. 22 explosion, according to the company.

The company released a statement of its preliminary findings Thursday afternoon, saying that because the mill was out of operation for an extended period of time leading up to the blast, a mixture of off-gases and air combined to make an explosive environment around a digester on site. The company won't outline exactly how long the mill was shut down before the blast, nor will it say why the mill was out of operation.

"The gas mixture, combined with one of several possible ignition sources, provided the necessary components for the incident," the statement said.

"The unusual set of circumstances set in motion a chain of events unlike any that International Paper had ever seen or heard of."

A portion of the mill has restarted, but the facility has not been in full operation since the explosion. In a document IP filed with the U.S. Securities and Exchange Commission, the company said the damage to the site was estimated at $50 million and it's likely the plant won't be fully operational for at least another three months.

Initially, the company said the blast was caused by a manufacturing process failure that released a mixture of wood fiber, water and pulping liquor into the surrounding area. During a town hall meeting weeks later with concerned citizens, representatives monitoring clean-up efforts said there was no way to know exactly what chemicals and components were in the air the night of the explosion.

IP said in its Thursday statement that because the mill had been shut down for so long before the explosion, there were no chips or liquor flowing into the digester at the time it exploded.

The impact of the blast was felt as far away as 10 miles, according to residents whose homes and vehicles were covered in the black liquor debris directly after the event, which occurred at about 7:40 p.m.

Clean-up crews in hazmat suits worked primarily in the most-affected Woodbury Circle neighborhood for weeks following the event in an effort to clean and remediate homes. The crews completed water, soil and air testing, but the company won't give a number as to how many residents expressed concern for their property or health through a hotline set up in the days following the blast.

While IP has released preliminary findings to its own investigation, the Occupational Safety and Health Administration and the State Fire Marshal still have not handed down their own investigative documents.