Several bomb threats have been reported around the country, including at 20 North Dakota hospitals, several Minnesota businesses and South Dakota schools.

Hospitals in Wishek, Elgin, and Tioga in North Dakota were among those reporting bomb threats or emergency situations on Thursday, Dec. 13. The hospitals locked down, evacuated or closed following the threats, though most resumed normal operation by Thursday evening.

Several businesses in Alexandria, Minn., and Sioux Falls, S.D., reported similar threats. Schools in Sioux Falls were also threatened.

The bomb threats arrived via email and demanded $20,000 in Bitcoin, an electronic currency, or else an explosive would be detonated, according to a news release from South Dakota Public Information Officer Sam Clemens.

The emails appear to be “a scam involving scare tactics” from one source, the release said. Police do not believe there is a threat to the public.

The FBI said in a statement that it was aware of "recent bomb threats made in cities around the country." The agency is in touch with law enforcement to provide assistance, it said, asking the public to remain vigilant and promptly report any suspicious activity.