Some 4000 tons of military grade explosives have gone ka-boom in Donguz, 40 km south of Orenburg (Russia), creating a huge vertical cloud that some describe as "mushroom-shaped".
A video is available from Russia Today:
Those 4,000 tons included 1,379 tons of 100mm shells, 400 tons of air bombs and 2,300 tons of 280mm reactive shells, the head of the military investigative committee announced.
It seems that children have been evacuated from schools and kindergarten and that there was some sort of advice for all residents in the nearby town to evacuate. However there is no information yet of possibly harmful chemicals or radioactive substances that could be a health hazard.
Even if the explosives are conventional, modern such weaponry often uses depleted uranium (a byproduct of nuclear energy industry) for increased penetration, being a major source of radioactive contamination wherever they explode, be it Gaza, Fallujah, Libya, Kosovo or Orenburg.
Notice anyhow that the term reactive shell means a type of warhead made of nanomaterials designed to fragment and burn upon explosion, causing greater damage, not anything radioactive in principle.
Sources: EneNews, Russia Today.