A state fire investigator has determined that the June 5 fire that damaged a wood shop at Two Bridges Regional Jail was accidental, Wiscasset Fire Chief T.J. Merry said. No one was hurt in the early morning fire.

An investigator from the state fire marshal’s office found that the fire started due to spontaneous combustion of linseed oil in a bucket at the shop, a three-bay garage where inmates do wood-working, authorities said.

The Route 1, Wiscasset jail’s approximately 168 inmates, from Lincoln, Sagadahoc, Waldo and Penobscot counties, and from the Maine State Prison, were making their beds and getting ready for breakfast when the jail went into lockdown, Two Bridges’ correctional administrator Mark Westrum said at the scene. About one-quarter of the inmates were evacuated to the facility’s gym, from the part of the jail building nearest the wood shop, Westrum said.

The shop sits about 100 yards from the building where the inmates are held. The fire did not travel to the main facility, Merry said.

The fire was reported just before 6 a.m. Thursday, Merry said. When he arrived, he saw heavy flames on the building’s south side, he said. The fire was knocked down within about 15 minutes.

“(There was) just a lot of overhaul and a lot of hard work ... to extinguish ... the remaining hot spots,” Merry said.

Firefighters from Woolwich, Alna and Bath helped Wiscasset firefighters at the scene. Crews from Edgecomb, Westport Island and Dresden manned Wiscasset’s fire station.

The building pre-dates the rest of the facility by about a year. It was built by Maine State Prison inmates as a transitional building for staff while the jail was under construction, Westrum said. The jail opened in 2006.

Inmates were last working in the shop at 2 p.m. on Wednesday, Westrum said. There, they make wood products for sale in a self-sustaining, non-taxpayer-funded program, Westrum said.

The jail recently opened a kiosk at the Wiscasset waterfront to sell the products. About $1,800 in items had been sold; Westrum was not yet sure when the building would be able to re-open and the program resumed.

“That building needs some good repairs,” Merry said.

“It’s a very unfortunate event,” Westrum said about the fire. “I don’t know what we’re going to do.”

Inmates make $1.25 an hour working in the shop, Westrum said. They get to keep a small portion of their wages to spend at the jail store; the rest goes toward paying any restitution and fines they owe in connection with their cases, and to room and board, he said.

In separate interviews, Westrum and Chief Merry praised firefighters’ efforts.

“All firefighters ... did a great job at extinguishing the fire with great help from our mutual aid companies,” Merry said.

“I’m very thankful that they were able to save the building,” Westrum said.