American authorities say an ongoing operation along their northern border has led them to revoke U.S.-issued travel visas for thousands of people, most of whom were headed to Canada to claim asylum.

Some, according to a U.S. State Department report, are associated with terrorist groups.

The revocations happened as part of what's called Operation Northern Watch, which focuses on criminal activity such as visa fraud, human smuggling and terrorist threats at the Canada-U.S. border.

Since the operation began in January 2015, authorities have revoked approximately 2,400 visas that were issued from 85 different American diplomatic posts abroad.

"Although some suspects have committed crimes in the United States, the vast majority of the individuals referred through Operation Northern Watch are individuals intending to claim asylum in Canada or have already claimed asylum," reads the annual report of the State Department's diplomatic security service (DSS).

"Included in this group were individuals with ties to designated terrorist organizations."

In an email, a U.S. State Department official told CBC News the DSS is unable to release information about the terrorist groups and any alleged ties people may have had with them.

The DSS also would not specify how many of the revoked visas belonged to people headed to Canada.

"When speaking to law enforcement, some of the identified subjects admitted that they either attempted to claim asylum in Canada or stated that it was their intention to claim asylum in Canada. For others, the diplomatic security service had reason to believe that they planned to claim asylum in Canada," wrote the official.

The DSS says every prospective traveller to the United States undergoes extensive security screening but that in some cases "derogatory information" surfaces after someone enters the country.

In late October, Public Safety Minister Ralph Goodale told CBC News how Canadian officials had identified trends where documents identified from certain U.S. embassies and consulates are being misused.

"We have asked them to go back upstream and examine the pattern of these travel documents being issued and how come the people to whom they were issued appear to have had no intention of staying in the United States, but were simply using the documents as vehicles to get into the United States and then make a beeline for the Canadian border," he said at the time.

Undermines narrative

National security expert Christian Leuprecht said Operation Northern Watch demonstrates how the U.S. understands and is acting on loopholes in its travel visa system.

"At the moment, the Americans realize there's a Canadian dimension to this," said Leuprecht, who teaches at Queen's University and the Royal Military College in Kingston, Ont.

Leuprecht said the annual report also undermines the long-standing narrative that people with ties to terrorist organizations easily enter Canada and head to the United States.

"There's not really much of a problem in terms of people coming from Canada to the U.S., certainly not since 9/11, because of all the measures we've put in place. But we continue to have a challenge with people who are inadmissible and who have ties to illegal organizations, who find their way to the United States and then make their way to Canada," he explained.

Karine Côté-Boucher, an assistant professor at the University of Montreal criminology school, cautions that terrorist ties aren't always as scary as they sound.

"What are those ties? To know someone or [be] related to [someone], is sometimes enough to put you on a terrorist watch list. We have kids in Canada who are on no-fly lists right now," she said.

Côté-Boucher added that just because someone used criminal means to enter Canada, does not mean they intend to do harm.

"Do they have criminal intent? That's different, right? That's a different question. There's nothing in there that suggests to me that people have criminal intent in Canada," she explained.

Travel visa harmonization

But Leuprecht believes, given the ongoing pattern of human migration, that it's time for North American leaders to take a co-ordinated approach to travel visas to prevent people from abusing the travel visa system.

After all, he said, Canada and the U.S. already share data on land, sea and air ports of entry.

"We probably need to start sharing data on people who request visas into North America, show that we can jointly assess whether the claims that people are making and the intelligence people are providing are effective, because we can see that people are trying to exploit the travel regime," he said.

For her part though, Côté-Boucher said she can't see a good reason to give up sovereignty over who gets to come to Canada. She explained how she feels Canada's tight border control mechanisms are partly responsible for the rise in irregular border crossings by migrants who are looking for a safe place to live.

"We have introduced so many border control mechanisms in North America right now that we have forced people to go through human smuggling networks, to go through visa fraud," said Côté-Boucher.

As for Operation Northern Watch, the DSS initiative has already expanded beyond its offices in New York State to Minnesota and Detroit as well as its regional security offices in Ottawa, Montreal, Vancouver and Toronto, where it works with Canadian authorities.

No one from the Canadian departments of Public Safety or Immigration responded to requests for more information about the operation.