BANGOR (AP) – A fresh batch of toxic red tide plankton is showing up in eastern Maine near the Canadian border and could reach dangerous levels that prompt more shellfish harvesting closures, officials said.

The latest bloom is appearing just as this summer’s massive red tide outbreak seemed to be subsiding.

In the past week, toxin levels in some shellfish samples from closed areas in Penobscot Bay have increased eightfold, said Darcie Couture, director of biotoxin monitoring for the Department of Marine Resources.

Other closed areas are being enlarged, with the northern boundary of one closure moved a few miles east from Youngs Point in Corea to Petit Manan Point in Steuben. Farther south, harvesting again has been banned in an area that had been reopened near Port Clyde.

Within the next week, red tide blooms could reach dangerous levels, particularly in the far eastern parts of the state that were spared the worst of the June outbreak.

“There’s a pretty significant bloom out there,” Couture said. “It looks like this will be the big hit for Down East Maine.”

A massive bloom of toxic red tide struck the New England coast in May following stormy weather that blew the phytoplankton from offshore waters to the coast. At its worst, the bloom forced the closure of a majority of the shellfish harvesting areas along the New England coastline from Maine to Cape Cod.

The red tide has diminished somewhat as of late. In Massachusetts, large coastal regions are being reopened, including new openings announced Wednesday.

In Maine, the worst-case scenario in the next few days would involve a storm moving from the northeast, with winds that could carry this newest bloom to shore, Couture said.

For the next couple of days at least, the National Weather Service is predicting winds from the northwest to southeast away from the shore for coastal eastern Maine.

But that doesn’t ease the concerns of DMR scientists. Couture said that she fully expects to see a new bloom soon, beginning Down East and likely expanding south and west along Penobscot Bay as it grows.

The plankton that causes red tide is found naturally throughout the Gulf of Maine. But when ideal conditions send it into reproductive overdrive, the resulting blooms produce toxins that can be deadly when birds, wildlife or people eat contaminated shellfish.

Filter feeders such as clams, mussels and oysters can take in so much toxin that eating them produces effects ranging from severe food poisoning to, in rare cases, death. No one in Maine has died of the condition, called paralytic shellfish poisoning, since the state started monitoring plankton blooms 50 years ago.