A massive fireball was recorded above Siberia, near Yekaterinburg, on November 14, 2014. The explosion apparently happened near the city of Rezh.
Various explanations have been raised. The Russian Ministry for Emergency Situations said it was an on ground explosion, but the Siberian Times, a local newspaper, noted that "the light was not accompanied by any sound". Regarding the meteoroid hypothesis, the Siberian Times also noted that "a local observatory indicated nothing fell from the sky on the day of the flash". Another hypothesis that was raised is the high-altitude nuclear explosion. An high-altitude nuclear test usually creates a very large fireball, because the absence of air allows for a maximum expansion of the fire. Such a test would not create a strong electro magnetic impulse in a period of intense solar activity (as Autumn 2014 was). The CTBTO has independent means to watch for underwater, underground and atmospheric nuclear tests, but not for extra-atmospheric nuclear tests - for that it relies on information that member States such as the USA would provide. Asked about the event, Mr. Patrick Grenard of the CTBTO only noted that, regarding high altitude nuclear tests, the CTBTO relies on communication of information from Member States. The fireball happened not far from Lesnoy, Sverdlovsk Oblast, a city which houses the Elektrokhimpribor plant known for making nuclear weapons. A conference of the Collective Security Treaty Organisation (CSTO) was held in Yekaterinburg in mid-November 2014 ; its topic was air/missile defence. Thus the fireball, if it was confirmed to be a nuclear explosion, could be understood as a test of Russian capabilities for ICBM interception. The mystery, however, remains.