Anti-vaccine mandate protesters in Ottawa received some help from their neighbors to the south, with the city’s police department saying on Wednesday that a “significant element” from the United States has been involved with funding and planning the event.

Thousands of people descended on Ottawa Friday to demonstrate against Canada’s efforts to curb the spread of COVID-19, including vaccine mandates and mask wearing. Many came in their big rigs, specifically protesting the rule that truck drivers who cross the border must be fully vaccinated. The Canadian Trucking Alliance says a vast majority of its members are fully vaccinated, and several people at the protest over the weekend “do not have a connection to the trucking industry.”

“They have converged in our city, and there are plans for more to come,” Ottawa Police Chief Peter Sloly said on Wednesday. All of the participants, he added, are “putting our city and our residents, our partners, and our officers at great risk.”

Officials said there is a core group of protesters remaining in Ottawa, The Washington Post reports, and many are honking their horns at all hours and blocking businesses. Over the weekend, the National War Memorial was vandalized, and a homeless shelter and soup kitchen said its staff was harassed by protesters and one of its residents was assaulted. There are several criminal investigations now underway into “threatening” and “illegal” behavior by protesters, police said, and three people have been charged. 

Prime Minister Justin Trudeau on Tuesday said Canadians are “shocked and frankly disgusted by the behavior displayed by some people protesting in our nation’s capital.” Sloly said on Wednesday police are “trying to be responsible, lawful, ethical, and measured. The longer this goes on, the more I am convinced there may not be a police solution in this demonstration.”