Katahdin Paper Co.’s Millinocket mill has stopped using a chemical that state officials say triggered a massive algae bloom in the Penobscot River last month, a company official said Tuesday.

Glenn Saucier, spokesman for East Millinocket-based Katahdin Paper, said the company stopped using phosphoric acid at the beginning of the month after identifying a suitable alternative for whitening the mill’s paper products.

Saucier said the company has no plans to go back to using phosphoric acid, the primary chemical culprit in a bloom of blue-green algae that affected a 75-mile stretch of the Penobscot.

“We put it in a tanker and moved it off-site,” he said. “That is our commitment. We don’t plan on using it, and if it’s off-site we can’t use it.”

Representatives of the Penobscot Nation and the Maine Department of Environmental Protection welcomed news of the mill’s transition, which followed several weeks of finger pointing over the events leading up to the algae bloom.

“I certainly hope they do take any measure necessary to prevent the algae bloom from occurring next summer,” said John Banks, director of the Penobscot Nation’s Department of Natural Resources. “If that’s what it takes, then they’re on the right track.”

Some types of cyanobacteria commonly known as blue-green algae can be harmful to humans and animals in higher concentrations. As a precaution, the leadership of the Penobscot Nation had advised tribal members to avoid swimming in or ingesting water from the Penobscot River during the bloom.

That advisory has since been lifted after no toxic strains of algae were found in several river water samples the Penobscots sent away for testing. The bloom apparently dissipated as temperatures dropped and the mill decreased its discharge of phosphorus into the river.

Dan Kusnierz, water resources program manager with the Penobscot Nation’s Department of Natural Resources, said he hopes the risk of another bloom has passed. But he pointed out that the river had a serious cyanobacteria bloom this week in 2001.

The recent bloom heightened tensions among Katahdin Paper, the state and the Penobscot Nation.

DEP officials criticized the mill for not notifying the agency that more phosphorus was being discharged into the river.

But tribal leaders blamed DEP officials for not attaching strict phosphorus discharge limits to the company’s license after a severe bloom in 2004. This summer’s bloom also came only weeks after a federal appellate court upheld the state’s ability to regulate water quality on rivers that pass through tribal lands, much to the dismay of Penobscot and Passamaquoddy leaders.

Andy Fisk, director of the DEP’s Bureau of Land and Water Quality, said department staff members are working to negotiate a settlement agreement with Katahdin Paper stemming from the algae bloom. They hope to send the proposed settlement agreement to the company soon, he said.

Katahdin Paper’s Saucier said the new compound being used to whiten the company’s glossy “supercalender” product costs up to two times as much as phosphoric acid. So far the alternative brightening agent seems to be just as effective, he said.

“It’s the right move, but it took us a little bit of time to figure everything out,” Saucier said.

Saucier said eliminating phosphoric acid should allow the company to meet phosphorus discharge limits set by the DEP after the algae bloom. Eliminating discharges altogether may not be possible, however, because small amounts of phosphorus still are needed in other stages of the papermaking process.

The Penobscot Nation’s Department of Natural Resources, meanwhile, has started using new screening tools that will help staff to detect a potentially toxic algae bloom earlier.