They are not quite of the carefully carved nature of the previous ones, but they are a mystery nonetheless.
They do not seem to be bottomless either, but the water and ice they contain, as well as sheer size makes it hard to investigate. Some attribute it to underground gas expanding due to climate change, but locals have reported a bright shaft of light the night one of them was formed. Also, they do not fit the bill for typical explosion craters.
We'll just have to wait and see as the story unfolds.
Also check out this Hole!
Sources:
http://www.iflscience.com/environment/scientists-get-first-look-inside-mysterious-siberian-crater
http://www.iflscience.com/environment/two-more-mysterious-siberian-craters-discovered
http://www.gizmodo.co.uk/2014/07/new-video-of-mysterious-giant-siberian-hole-filmed-by-investigation-team/
