The Brussels prosecutor’s office revealed on Wednesday the nature of the substance that was sent last November to government buildings, including the office of De Croo.

Belgian media reported that an unnamed member of De Croo’s office had received hospital treatment after injuries to their hands after opening the letter.

It is reported to have been discovered on 22 November, two days after similar packages were found at the office of the interior minister, Annelies Verlinden, and the headquarters of the state security service. Another person was put into quarantine as a precaution, but not hurt, after these discoveries.