Canada joined a growing number of countries on Monday in closing its borders to most foreigners in an effort to stem the spread of the coronavirus.

While the federal government stopped short of restricting citizens of the US from entering the country, Justin Trudeau, prime minister, said that measure had not been ruled out, as preliminary provincial data indicate that a growing number of cases in Canada can be traced to the US.

“At this point we are closing our borders to all non-Canadian and non-permanent residents of Canada,” he said.