The desperate manhunt for suspected Maine mass shooter Robert Card has extended to Canada, with authorities issuing an alert for the “armed and dangerous” trained marksman — as it was revealed his online search history contained conspiracy theories, including about President Biden.

The Canada Border Services Agency said it issued the alert to officers along the US-Canada border to “ensure the safety and security of Canadians and protect Canada’s borders against any threat or [attempted] legal entry.”

It came three days after 18 people were killed and more than a dozen others injured in a Wednesday night shooting spree at multiple sites in Lewiston, Maine.

The mayor of a border town in Canada also said he was aware of American authorities at the border “checking people leaving the country” and said Canadian police are “doing the same as we speak,” according to Global News.

St. Stephen Mayor Allan MacEachern put out his own alert to remind residents to be vigilant.

“We’re going to make sure everyone knows: Keep your eyes and ears open for any strange activity,” he told Global News.

The Canadian alerts came as in the US more than 350 state and federal law enforcement officials continued the manhunt for Card, thought to be the gunman caught on surveillance footage during the massacre of 18 people in two different locations in Lewiston, Maine, late Wednesday.

The Coast Guard announced on Thursday it dispatched a boat crew from Boothbay Harbor, and a wing plane from Cape Cod to assist in the search efforts.

Card, a skilled outdoorsman, and trained US Army Reserve marksman, owns a 12-foot Sea-Doo jet ski registered in his name and had previously registered for a 15-foot bay liner boat, according to documents obtained by CBS News.

But after hours of searching, authorities found “nothing out of the ordinary,” Chief Petty Officer Ryan Smith, who is in charge of the Coast Guard’s Boothbay Harbor Station, told KATV.

Rick Goddard, a longtime neighbor of Card’s, told The Post he is “capable of hiding for a long time if he doesn’t want to be caught.”

“It’s his stomping ground,” Goddard said of Card’s hometown in Bowdoin.

“I mean, he grew up here. He knows the area really well. He’s capable of hiding for a long time if he doesn’t want to be caught. There’s a lot of places you can be in the woods and never be seen,”

“It’s his stomping ground,” Goddard said of Card’s hometown in Bowdoin.

“It’s really dense, thick woods. If you know the area, there’s a lot of places you can hide… you could never see something like that from an airplane or helicopter.

At least 18 people are dead and over a dozen injured after a gunman opened fire at two separate locations in Lewiston, Maine.

Police identified the possible suspect as Robert Card, 40, and believe he may have been driving a white Subaru Outback, which was later located in Lisbon, about 8 miles away from the shooting sites, according to CentralMaine.com.

Residents in Lisbon were also ordered to shelter in place, with authorities warning that Card may be armed and dangerous.

Maine State Police advised local residents and businesses to lock their doors and shelter in place.

On Wednesday night, emergency personnel were called to separate shootings at Sparetime Recreation bowling alley and at Schemengees Bar and Grille Restaurant, according to the Sun Journal.

The death toll nearly matches the annual number of homicides in the state of Maine — with 29 homicides being reported in 2022.