WINDSOR, Ontario — Canadian police moved in Saturday to remove protesters who have disrupted Canada-US trade at a major bridge border crossing.

Protesters at the busiest crossing between the United States and Canada remained overnight despite new warnings to end the blockade that has disrupted the flow of goods between the two countries and forced the auto industry on both sides to roll back production.

A city bus and school bus arrived at the scene Saturday morning and police moved in formation toward them. One of the protesters used a megaphone to alert others that police were coming for the demonstrators, who are protesting against Canada’s COVID-19 mandates and restrictions. There is also an outpouring of fury toward Prime Minister Justin Trudeau.

“The Windsor Police & its policing partners have commenced enforcement at and near the Ambassador Bridge. We urge all demonstrators to act lawfully & peacefully. Commuters are still being asked to avoid the areas affected by the demonstrations at this time,” police tweeted.

About 20 protesters huddled together while others remained in pickup trucks and cars as police asked drivers to leave. Tow trucks and ambulances were stationed near the protest.

“The illegal blockades are impacting trade, supply chains & manufacturing. They’re hurting Canadian families, workers & businesses. Glad to see the Windsor Police & its policing partners commenced enforcement at and near the Ambassador Bridge. These blockades must stop,” Federal Innovation Minister Francois-Philippe Champagne tweeted.

A judge on Friday ordered protesters at the Ambassador Bridge over the U.S.-Canadian border to end the blockade that has now entered a sixth day.

On Friday, Ontario Premier Doug Ford declared a state of emergency in the province that will allow his cabinet to impose $100,000 fines and up to one year in jail as punishments against people who continue to illegally block roads, bridges, walkways and other critical infrastructure.

Chief Justice Geoffrey Morawetz of the Ontario Superior Court issued an injunction giving protesters blocking cross-border traffic until 7 p.m. Friday to clear out. However, the deadline came and went.

Windsor police immediately warned that anyone blocking the streets could be subject to arrest and their vehicles could be seized.

The news was met earlier with defiance by protesters.

At the Ambassador Bridge, an unidentified person grabbed a microphone and addressed the crowd, asking if they wanted to stay or leave when the deadline rolled around. By a show of applause, it was agreed they would stay. “OK,” the man said. “Let’s stand tall.” The protesters responded by singing the Canadian national anthem.

The Ambassador Bridge is the busiest U.S.-Canadian border crossing, carrying 25% of all trade between the two countries. The standoff comes at a time when the auto industry is already struggling to maintain production in the face of pandemic-induced shortages of computer chips and other supply-chain disruptions.

While the Canadian protesters are decrying vaccine mandates for truckers and other COVID-19 restrictions, many of the country’s infection measures, such as mask rules and vaccine passports for getting into restaurants and theaters are already falling away as the omicron surge levels off.

Pandemic restrictions have been far stricter in Canada than in the U.S., but Canadians have largely supported them. The vast majority of Canadians are vaccinated, and the COVID-19 death rate is one-third that of the United States.