PARIS – Firefighters Thursday night made their way to the heart of a smoldering fire in a massive Pine Street warehouse, removing stockpiles of rolled paper as their battle entered its second day.

The blaze began around 1 p.m. Wednesday at New England Public Warehouse Logistics, where an estimated $10 million worth of paper pulp was stored. Firefighting efforts were expected to last at least into Friday morning.

“We’re at the point now where we’re chipping away,” said Scott Parker, public information officer and director of the Oxford County Emergency Management Agency. “It will take time to work our way through the place.”

As of Thursday night, 44 fire departments in western and southern Maine had sent about 150 firefighters and equipment to quell the roaring fire that was fueled by 20,000 tons of paper pulp from Canada on its way to Maine mills.

Most of the firefighters were volunteers who took time off from their jobs to fight the stubborn blaze.

When the fire broke out in the 187,000-square-foot warehouse on Wednesday, welders were repairing a section of the roof near a tall pile of paper in the area where the fire started.

It sent 15 employees and company President Drew Gilmore of Cape Elizabeth running from the flames.

On Thursday, a 70- by 260-foot center section of the roof collapsed into the warehouse, a former leather-tanning plant.

Construction crews worked on the back of the building throughout the evening, trying to remove a burning rail car loaded with paper and a rail car that was blocking the entrance to the rear of the building, which had collapsed, said York County Emergency Agency Director Bob Bohlmann, who relieved Parker on Thursday night.

Once crews got the rail cars out, that portion of the building would be taken down to let firefighters get to the remaining fire, Bohlmann said.

“The whole warehouse isn’t damaged,” he said.

Paris Town Manager Sharon Jackson, who was at the scene Thursday, said the building was valued at $3.1 million by the town.

“We’re trying to get to the seat of it on the backside of the building,” said Paris Fire Chief Brad Frost, who was expected to be relieved as incident commander Thursday night after 30 or more hours at the scene. He had assistance Thursday from Portland Fire Chief Fred Lamontagne Jr.

Frost said firefighters were working in shifts of 12 to 14 hours at a time. “I wouldn’t say they’re getting plenty of rest, but they’re cycling people in,” Parker said.

Crews were positioned cautiously around and in the building to ensure their safety.

“They made the decision early on not to send anyone into harm’s way,” said Lt. Michael Dailey of the Paris Police Department. “It’s been very fortunate.”

Parker said there were no indications that chemicals were a problem.

“We feel very comfortable it’s not a (hazardous-material) situation,” he said.

Parker said some forklifts had been salvaged from the building and nearby administrative and storage areas should be relatively unaffected by the fire.

Water was being pumped from the Little Androscoggin River behind the warehouse after crews initially tapped into municipal hydrants.

Oxford Hills Middle School and Oxford Hills Christian Academy on East Main Street were closed Thursday due to portions of Pine and East Main streets being closed by the fire. SAD 17 Superintendent Mark Eastman, who was at the command center Thursday, said the middle school would remain closed Friday to students, but staff would be allowed in.

“It is a disruption,” Eastman said. But safety was of primary importance.

All other SAD 17 schools will be open Friday.

Dailey said both Route 26 and the St. Lawrence and Atlantic Railroad, which had been closed after the fire, were opened Thursday morning. Pine Street remained closed, along with East Main Street from Market Square to Oxford Street. Traffic to Route 119 was being detoured over Paris Hill Road and Hill Street.

The State Fire Marshal’s Office is expected to make a statement Friday about the cause of the fire.