COOSA, Georgia (From news reports) -- Investigators were back on the scene Monday, March 16, to determine the origin of an early morning fire that caused extensive damage to the International Paper mill in Coosa.

"It was as bad a fire as I've ever seen out there," said Rome-Floyd County Fire Chief Troy Brock on Sunday.

Battalion Chief Clay Walker, who was with the first responding units, said the location of the fire made it difficult to get to. Once firefighters were close to point of origin, they had to back out and regroup because a portion of the roof and wall had collapsed.

The fire was so hot that it expanded the roof trusses, according to Division Chief Clete Bonney, and that helped push out a side wall of the building.

"It caused extensive damage to the production lines," Bonney said.

Fire Marshal Mary Catherine Chewning said one mill employee was taken to the hospital for treatment of smoke inhalation but their condition did not appear to be serious.

"We are grateful all of our team members and contractors are safe with no serious injuries reported," said mill spokesperson Jenna Guzman in a Sunday statement.

Walker said the mill sprinkler system helped contain the fire -- but at least five fire units were on the scene until almost 4 a.m. Sunday, making sure the blaze was out and there were no hot spots.

Debris was still falling from the roof at 3:30 a.m. as the building appeared to be settling at the end of the fire, Bonney added.

Chewning said the nature of the site, coupled with the collapse and the rain on Sunday made it very difficult to get in to investigate. She said International Paper would be flying in personnel from corporate headquarters to assist with the investigation.

The point of origin appeared to be in the area of the two paper machines inside the building, Chewning said, but she could not pinpoint a specific location Sunday.

Guzman said that it was entirely too early to know what kind of impact the fire will have on production at the mill, which makes linerboard.

The mill has has been the focus of major technological upgrades and close to $300 million in capital investment by International Paper over the last seven years.