BANGOR (AP) – A Millinocket paper mill is to blame for an unusually large algae bloom in the Penobscot River that prompted the Penobscot Nation to advise tribal members to stay out the river until further notice, state officials said.

The blue-green algae bloom has not been determined to be toxic, so there’s no state-issued health advisory. But a sample from the algae bloom has been sent away for further analysis, state environmental officials said.

Penobscot leaders issued an advisory late last week recommending that tribal members and their pets stay out of the river and warning against drinking water from Dolby Pond near Millinocket to the coast.

“We’re really taking the precautionary approach in the event that it is toxic,” said John Banks, director of the Penobscot Nation’s Department of Natural Resources.

The Maine Department of Environmental Protection issued a notice of violation last week to Katahdin Paper Co.’s Millinocket Mill for phosphorus discharges.

Phosphorus, which is used in pulp production, can help trigger large blooms of the potentially toxic blue-green algae.

Blue-green algae is comprised of a type of bacteria. Most blooms are not harmful.

However, some blooms can release toxins that can irritate the eyes and skin or cause gastrointestinal problems in people and pets.

‘Very discouraging’

Penobscot Nation Chief Kirk Francis says the bloom is symptomatic of what he said are larger problems of state oversight of water quality in the Penobscot.

After a 2004 blue-green algae bloom, Katahdin Paper agreed to limit phosphorus discharges. But discharge levels were never written into the permit.

“Because nothing was done in 2004, we have this (bloom) in the river once again,” Francis said. “I have a camp up on the river and to have to question whether to take my family out on the river is very discouraging.”

David Courtemanch, director of environmental assessment at the DEP, acknowledged that it is unusual to have a bloom extend over so large a river.

Nonetheless, he does not believe state-issued health advisories against swimming in the Penobscot are necessary at this point.

“I know of no cases, even when the blooms were worse, when we’ve had illnesses reported,” he said.