STRONG — A state fire investigator said roughly $8 million damage was done to a wood pellet manufacturing mill after an explosion in the woodchip dryer early Saturday.

Three people were injured and were treated at a hospital and released the same day, Sgt. Ken Grimes of the Office of the Maine State Fire Marshal said Monday.

“We are not exactly sure of the cause of the combustion explosion,” Grimes said. Where it is an accident, engineers hired by the company will try and determine exactly what happened, he added.

The Geneva Wood Fuels plant, which is owned by an Illinois-based investment group, went online earlier this year. The mill site was formerly Forster Manufacturing on Norton Hill Road, which made toothpicks and other wooden items, before it closed in 2002.

“There are lot of different components involved,” Grimes said of the pellet-manufacturing operation. “By looking at it, some components were destroyed and some were not.” The woodchip dryer and supporting equipment were destroyed, he said, adding that the mill is not operational at this time.

Two of the three injured workers had been on the roof when the explosion occurred, and the plant manager was in the control room when the glass blew out of it, Grimes said. The employees were starting the mill back up after it had been down for maintenance that did not involve the dryer, he said.

The house next to the mill had 11 windows damaged, ranging from cracked sills to broken single or double-paned glass, Grimes said.

Dispatchers at the Franklin County Communication Center in Farmington, which is 8 miles away, heard the 1:30 a.m. blast.

A plant representative was not available for comment Monday.

dperry@sunjournal.com