Dozens of bomb threats — all believed to be unfounded — were reported in major cities across Canada and the United States on Thursday. Officials from both countries said they believe the threats — clumsily written emails demanding $20,000 US payments of bitcoin — may have all come from the same source.

Some of the emails had the subject line: "Think Twice."

Police in Toronto said multiple threats were being investigated across the city Thursday afternoon, including one involving the busy downtown King subway station, which was evacuated. Service at the station resumed within the hour.

In the Montreal area, police said they responded to threats against at least five businesses.

Police in Ottawa, Winnipeg, Calgary, and Edmonton, as well as smaller cities across the country, all dealt with similar incidents.

In British Columbia, the U.S. Consulate in Vancouver said in a statement that it was aware of 15 bomb threats made in the province. Vancouver police said they were also aware of numerous threatening emails received across the city.

In a statement before the threats were deemed to be unfounded, Public Safety Canada advised Canadians to "follow the direction of local law enforcement and to report anything suspicious to them."

Threats received across U.S.

The threats come on the same day that online bomb threats were received in cities across the U.S.

U.S. authorities said Thursday that threats sent to dozens of schools, universities and other locations appeared to be a hoax.

At this time, it appears that these threats are meant to cause disruption and/or obtain money. We’ll respond to each call regarding these emails to conduct a search but we wanted to share this information so the credibility of these threats can be assessed as likely NOT CREDIBLE. —@NYPDnews

The New York City Police Department said the emailed messages were meant to cause disruption and compel recipients into sending money, and are not considered credible. Officials in Georgia, Louisiana, Alaska, Idaho and Florida also said they believed them to be unfounded.

Some U.S. schools were closed early and others were evacuated because of the threats.