Radek Pokornik, a spokesman for the National Institute for Nuclear, Chemical and Biological Protection that conducted tests on the suspicious envelope said today it contained "a cyanide-like material in a life-threatening amount."
Pokornik declined to give further details,
The minister, Milan Chovanec, previously said the envelope was sent to him at the ministry from an unspecified Nordic country. It was intercepted before anyone could be exposed.
Chovanec said the envelope, received Tuesday, didn't contain any message.
The country's foreign ministry, the government and the presidential office recently also received suspicious letters but with no poison. Chovanec said the latest case likely has nothing to do with the previous ones.