ORRINGTON — Firefighters hampered by smoke and steam battled a stubborn trash fire in a fuel storage area of the Penobscot Energy Recovery Co. here for about eight hours Sunday.

Trucks from Orrington, Brewer and Holden responded to the flames, and were assisted by PERC’s first response squad. Television monitors inside the storage area spotted the flames at 9:45 a.m. and authorities were promptly alerted.

Officials were not certain Sunday afternoon what set dry demolition debris and other dry waste materials afire.

Bob Field, plant manager, said the fire was located in the southeast end of a building 100 feet wide and 200 feet long. He speculated that household cleaners or hot materials coming from the waste-to-energy processors may have caused the flames. “We’ll probably never know,” Field added.

Firefighters got in early and subdued the flames within an hour and a half of their arrival. But the fire smoldered beneath layers of rubbish, and firefighters were unable to put it out, said Orrington Fire Chief Les Grover.

“There’s so much smoke and heat that you can’t get in there to do anything,” Grover said at the scene. “You’re lucky if you can see 20 feet in there.”

Smoke and steam plagued the effort of rotating crews attempting to get at the fire from inside the building. “They can’t stay in that heat for too long today,” he said of firefighters entering the building equipped with breathing apparatus.

The fire was still smoldering about 6 p.m.

Grove said that if the structure had been equipped with ventilation units fire crews could have cleared the scene much sooner.

To contain odors that might seep into the community, Field said, the structure was built tightly, allowing for little ventilation. A concrete wall 20 feet tall wrapped around the burning materials, which made tackling the fire increasingly difficult.

Firefighters cut holes in the roof and the side of the building to release smoke and steam.

“As soon as we can get the smoke and steam cleared out, we can get in there,” said Field, adding that the plan was to spread, soak and restack the materials.

There have been other fires at the PERC plant, but their locations enabled the plant’s first response team to quell flames before other fire departments arrived. The location of Sunday’s fire was inaccessible, however, and more difficult to contain.

Field added that the fire will not interfere with operations at the plant. He planned to warm up the boilers Sunday night, and said he expected to receive Monday’s waste deliveries as usual.