PORTLAND — The closing of Bucksport paper mill will be delayed until the end of December, when more than 500 people are expected to lose their jobs.

Verso Paper Corp.’s Bucksport mill was initially set to shutter on Dec. 1. That’s now the day production at the mill will begin to shut down, company spokesman Bill Cohen said. Production will be over by Dec. 4, and cleanup and mothballing will begin, he said.

Cohen said the company made the extension because the shutdown of the mill was unlikely to be finished by the end of this month. The mill’s workers will remain on the payroll until Dec. 31, he said, adding that cleaning and winterizing the mill will likely take most of December.

“When we looked into the final schedule and how long it would take us to clean up and winterize and mothball the mill, it was clear we could not get it all done by next Monday,” Cohen said.

The company’s unions and employees are aware of the decision, which was made Tuesday, Cohen said.

The mill employs 570 people and its taxes make up more than 40 percent of Bucksport’s town budget. The October announcement of the mill’s closure rattled the state’s paper industry, which was also reeling from Great Northern Paper’s bankruptcy filing. That mill, in East Millinocket, is slated for auction in December.

Verso said prior to the announcement of the mill’s closure that the facility is not profitable.

Emery Deabay, president of the United Steelworkers Local 1188 union at the mill, said workers at the Bucksport facility were anticipating the extension of the mill shutdown. The news doesn’t change much for workers who will still be out of a job, he said.

“I’m looking at it the same way — to the workers on the floor, this is stuff they already knew,” Deabay said.

The mill sits at the head of Penobscot Bay in Bucksport, about 120 miles north of Portland. It has been there for more than 80 years.