A Canadian fisherman's association is reporting that U.S. Border Patrol agents have stopped and questioned multiple Canadian fishermen in waters that are the subject of an ongoing territorial dispute.

Canadian officials are investigating reports about two vessels specifically, stopped on June 24 and 25, where American agents claimed to be "looking for illegal immigrants," according to the Canadian outlet CBC News. Laurence Cook, chairman for the Grand Manan Fishermen's Association, which is based in New Brunswick, Canada, said at least 10 boats had been stopped in a two week period in the area around Machias Seal Island. The island lies about 10 miles offshore between the Gulf of Maine and the Bay of Fundy.

A statement from the association released Wednesday said the waters have been fished by both U.S. and Canadian crews for years. The group said it's their understanding that the recent stops are part of a "regular exercise being conducted along the U.S. marine border," and said it looked forward to continuing a "respectful and cordial relationship" with its U.S. counterparts.

Get Breaking News Delivered to Your Inbox

U.S. officials told CBC News in a statement that the border agents were in the area to "enforce immigration laws and other violations of federal law."

U.S. Customs and Border Protection confirmed in an email to CBS News that 21 Canadian vessels have been "interviewed" so far this year in the Houlton Sector, spanning along the Maine coast. "Border Patrol does not board Canadian Vessels without consent or probable cause and only conducts interviews as a vessel runs parallel to it, bow to stern," it said.

Without directly addressing the territorial dispute, CBP added that it "will continue to conduct operations in the waters off the Coast of Maine in jurisdictional waters of the United States."

On its website, CPB describes its Air and Marine Operations as conducting its mission "at and beyond the border." According to the Grand Manan Fishermen's Association, "Canada's sovereignty over the area is long standing and has a strong foundation in international law," although it notes the United States disputes Canada's claim.