Canadian officials and experts believe that the jump in illegal crossings has been fueled primarily by immigrants arriving in Canada from India on tourism or other temporary visas.

In a characteristically bombastic threat to slap hefty tariffs on Canadian and Mexican imports to the U.S. once he takes office next year, president-elect Donald Trump said he was motivated by border issues between those countries and his own.

The president-elect’s opening salvo in trade and border talks with the United States’ neighbors is casting a harsh light on the North American alliance.

President-elect Donald Trump vowed Monday to slap punitive tariffs against Canada, Mexico and China, citing allegations that drugs and undocumented immigrants were entering the United States via those countries.