Police in Windsor, Ontario, began to clear protesters who continue to occupy a vital Canada-U.S. trade corridor on Saturday, less than a day after a judge granted an injunction to end the blockade that has crippled North America’s well-knitted auto industry.

Tractor-trailer traffic has been blocked since late Monday from crossing the Ambassador Bridge from Windsor to Detroit. All Canada-bound bridge traffic from the U.S. has also been blocked since late Monday.

About 15 trucks, cars and vans blocked traffic in both directions Saturday afternoon, choking a key supply route for automakers.

The standoff continued into Saturday evening.

“We urge all demonstrators to act lawfully & peacefully,” Windsor Police said in a Twitter post, asking commuters to avoid the areas affected by the demonstrations. The police action came more than 12 hours after a court order to ended the blockade came into effect.

While police have successfully pushed back protesters from the foot of the Ambassador Bridge, more people were streaming into the area and the operation appeared to have stalled.

As the afternoon dragged on, some Canadians questioned what was behind the delay, given the order issued by a court on Friday to end the blockade and the imposition of a state of emergency declared by Ontario authorities.

“It would essentially send a message that the state is not able to retain control, where it’s attempted to do so,” Michael Kempa, an associate professor of criminology at the University of Ottawa, told CBC News.

“The longer this drags on, the longer people have the idea that what they are doing is not an illegal protest,” he said.

Earlier in the day, police in black uniforms with yellow vests moved behind the protesters’ vehicles and, accompanied by police cruisers, slowly advanced on protesters, pushing them back from the bridge entrance. The number of demonstrators had thinned to roughly two dozen early on Saturday from about 200 on Friday night. Tow trucks are on site to move vehicles.

“We are opening up this intersection to traffic. If you fail to comply with our instructions you will be arrested,” police told the crowd via a loudspeaker.

Protesters were seen moving back in a noisy but peaceful retreat, dismantling tents and barbecues.

Canadian Prime Minister Justin Trudeau has promised President Joe Biden quick action to end the crisis, and on Friday a Canadian judge ordered an end to the blockade of the bridge, North America’s busiest land border crossing.

“The Windsor Police & its policing partners have commenced enforcement at and near the Ambassador Bridge. We urge all demonstrators to act lawfully & peacefully,” the police said in a tweet at 8:18 a.m. EST Saturday. “Commuters are still being asked to avoid the areas affected by the demonstrations at this time.”

At least four buses are on site as the protests continued for a sixth day on Saturday. Video posted by local media outlets show some protestors leaving the scene.

The situation appeared peaceful, according to several social media posts and a live Youtube feed. Photos show strategically placed uniformed police officers at the entrance to the bridge, staring down the few protestors who remained.

The order went into effect at 7 p.m. EST on Friday, but five hours after the deadline, some 100 protesters were milling around the entrance to the bridge, waving Canadian flags.

While the number of protesters and police dropped as the night progressed, demonstrators continued to block the bridge with trucks and pickup vans, preventing any flow of traffic in either direction.

Protesters sang the Canadian national anthem and midnight, and some shouted “Freedom!”

Police, who started to gather in a parking lot a few blocks away from the protesters late Friday, began handing out pamphlets that outlined penalties under Ontario’s emergency order, which took effect at midnight.

Trudeau earlier told reporters that no action was off the table.

Earlier Friday, the Ontario Superior Court granted an injunction designed to end the six-day blockade of the Ambassador Bridge in Windsor, Ontario, as assembly plants in Ontario and Michigan continue to curtail production due to parts shortages.

The motion for injunction, filed by the Automotive Parts Manufacturers’ Association, with the City of Windsor and the Ontario Ministry of the Attorney General participating as intervenors, was heard Friday afternoon.

Lawyers for the APMA, city and province argued the blockade is causing ongoing and irreparable harm to Ontarians and businesses in the province, pointing to lost automotive production translating into tens of millions of dollars.

Chief Justice Morawetz said he was satisfied the case for the injunction was made and granted the injunction after about 4 ½ hours of submissions. The order will take effect at 7 p.m. ET Friday, he said, giving individuals the opportunity and time to clear the area.

The injunction hearing followed a declaration of emergency by Ontario Premier Doug Ford Friday morning, which could lead to stiff fines and jail time for blockaders in both Windsor and others dug in in Ottawa.

On Thursday, Windsor Mayor Drew Dilkens said growing ranks of Ontario Provincial Police have been arriving in the Windsor throughout the week and the city will have the resources necessary to remove their protestors and their vehicles. He also said Michigan Gov. Gretchen Whitmer has offered heavy equipment to assist with vehicle removal.

Dilkens did not give a clear timeline for enforcing the injunction on Thursday, saying the city continued to hope for a peaceful solution, but that it would be prepared to “move in” if necessary.

More police on site

Dilkens said on Thursday that if a peaceful approach fails, the city will have the resources to remove the protestors and their vehicles, drawing on assistance from the Ontario, and perhaps Michigan, governments. The city also has requested help from the RCMP.

The Ontario Provincial Police had much stronger and more visible presence in the area Friday.

With auto parts shipments across the Ambassador Bridge at a standstill, numerous assembly plants across Ontario shortened shifts this week, sending workers home because of a lack of parts.

Shane Wark, assistant to Unifor President Jerry Dias, said the blockade is just the latest issue in a tough couple years for Ontario’s auto workers.

“There’s been a whole, just relentless amount of layoff weeks that have occurred across the auto parts and the OEM assembly plants,” Wark told Automotive News Canada.

Wark said Unifor does not question the right to protest, but the blockade has “gone beyond that” and is harming workers and their families.

Meanwhile, there is mounting concern that the blockade will damage Canada’s reputation as a reliable trading partner as well as the competitiveness of its auto industry.

Competition for auto investment especially as the industry moves toward electrification is intense, Brian Kingston, president of the Canadian Vehicle Manufacturers’ Association, said at a news conference Thursday.

“When issues like blockades arise, it is a worry.”

Reuters and David Kennedy of Automotive News Canada contributed to this report.