Giant Sinkhole in Dagestan

Sinkhole near the village of Gurbuki Karabudakhkent in Dagestan. Scientist are trying to find out what caused this giant sinkhole.
UPDATE: The hole has been mesured to be no more than 30 meters. A young woman was saved at the same time. She was THROWN down there by her husband. The sinkhole is not new and has been known by the locals.