Nick Redfern: Tunguska & Crashed UFOs

Early on the morning of June 30, 1908, numerous people in the region of Tunguska, Russia, witnessed a large column of blue light moving deliberately across the sky. Approximately ten minutes later, the sighting was followed by the sound of a massive explosion that decimated the area, and caused damage hundreds of miles away from the presumed impact site of whatever it was that had earlier been seen in the sky. What do we know now?