Singer Chantal Kreviazuk changed the lyrics of the Canadian national anthem during the 4 Nations Face-Off championship game between the US and Canada on Thursday, adding further fuel to a contest already layered with political tension.

Before the puck drop at the inaugural 4 Nations Face-Off championship game in Boston, multiple fights had already broken out between Team USA and Team Canada fans in the lead up over the weekend. On Thursday, the night of the final, tensions were high as singer Chantal Kreviazuk took to the ice to sing Canada’s national anthem, “O Canada.”

Canadian hockey fans began booing the American national anthem at Bell Centre in Montreal when Team USA played there on Saturday — sparking three fights to break out in the first nine seconds of the game, which the US won 3-1 with Canadian Prime Minister Trudeau in attendance.

Canadian fans booed the American national anthem when the teams met in a round-robin match in Montreal, which was followed by three fights in the first nine seconds of the game.