Authorities in Poland have arrested four people in connection with an alleged plot to mail explosives to Canada and the United States.

In a media statement, Poland’s National Prosecutor’s Office says it began an investigation on Aug. 5, 2024 based on information obtained by the country’s Internal Security Agency, Poland’s domestic counterintelligence and security service.

The group’s plans involved “sending parcels containing camouflaged explosives and dangerous materials via courier companies to European Union countries and Great Britain, which spontaneously ignited or detonated during land and air transport,” the statement alleges.

“The group’s goal was also to test the transfer channel for such parcels, which were ultimately to be sent to the United States of America and Canada.”