The U.S. government has issued a report warning its contractors with classified security clearances of the threat of Canadian coins with tiny radio transmitters hidden inside.

Further details remain classified as the Department of defense refuses to speculate or release information on where the coins were found, or who might be responsible.

Top suspects include nation states said to run active espionage in Canada, China, Russia, and France. In related news, the CIA admits to using US Silver Dollar coins to smuggle.