"Silent but deadly"
That's the first thing that came to mind for me too.
Strontium, uranium and plutonium found in train to Caucasus
According to daily Stavropolsky Meridian, suspicious cargo was discovered in the train no. 389 on its way from Moscow to Mineralniye Vody, not far from Chechnya.
The revealed leaden containers were found in the luggage car of the train and contained radioactive materials like strontium, uranium and plutonium. Total weight of the containers was 20kg. The covering documents mentioned only the sender The Ministry of Nuclear Industry and the receiver Ingushetia State University. The radioactive materials were enough to make a ”dirty bomb”, the FSB specialists said to the newspaper.
http://www.bellona.no/en/international/russia/incidents/35545.html