Passage in both directions at Saint Bernard de Lacolle in Quebec was blocked shortly after 9:00 am (local time) following a "threatening telephone call aimed at customs," according to Ingrid Asselin of Quebec's national police agency.
She told AFP that all buildings were evacuated and an investigation was still ongoing two hours after the closure of the checkpoint, located about 60 kilometres south of Montreal on the border between Quebec province and the US state of New York.
The agency was encouraging travelers to reroute to nearby border crossings, one located 20 kilometres to the west and another 50 kilometers to the east.
More than two million visitors cross at the Saint Bernard de Lacolle checkpoint each year.