The U.S.-Canada border is the likely path for terrorists to invade the country, according to top national security experts and Congress’ most comprehensive review of America’s 19,000 miles of coasts and land borders.

“The nexus between known or suspected terrorists in eastern Canada and the northern parts of the U.S. represent a significant national security threat,” said a new report from the Senate Homeland Security and Governmental Affairs Committee, a conclusion made before Canada decided to settle 25,000 Syrian refugees by March.