Protesters blockaded a third U.S.-Canada border crossing on Thursday, escalating a crisis that's leading automakers to cut production, weighing on the economies of both countries and prompting U.S. officials to call for their Canadian counterparts to intervene.

The Royal Canadian Mounted Police said Thursday that the Emerson crossing between Manitoba and North Dakota was "shut down," after a large convoy of vehicles and farm equipment blocked traffic in both directions. Demonstrators protesting vaccine mandates and coronavirus restrictions have also blockaded border crossings at Coutts in Alberta and the Ambassador Bridge.

That bridge, which connects Windsor, Ontario, and Detroit, is the busiest land crossing on the border, and a key conduit for the auto industries on both sides. The mayor of Windsor said Thursday that the city and auto groups were seeking an injunction to end a blockade by protesters that for several days has snarled the crossing and the nearly $300 million in daily commerce that crosses it. Ford and General Motors have said they've already cut production and canceled shifts at some sites.

As the crisis deepened, officials in the United States called on their Canadian counterparts to get the demonstrations under control. The self-styled "Freedom Convoy," now heading into its third weekend, has paralyzed the Canadian capital. It has blockaded crossings and caused delays at crossings that remain open.

"It is imperative that Canadian local, provincial and national governments de-escalate this economic blockade," Michigan Gov. Gretchen Whitmer, D, said in a statement Thursday. "They must take all necessary and appropriate steps to immediately and safely reopen traffic so we can continue growing our economy, supporting good-paying jobs and lowering costs for families."

The White House said Thursday it was "monitoring" the situation at the border "very closely" and that Cabinet officials were "engaged around the clock to bring this to a swift end."