Among other theories, an article in SP Times [the first reference in the wikipedia article, en: http://www.sptimes.ru/story/25093 http://www.sptimes.ru/story/25

Among other theories, an article in SP Times [the first reference in the wikipedia article, en: http://www.sptimes.ru/story/25093 http://www.sptimes.ru/story/25093] suggests a possibility of avalanche. Combined with the guess that the radioactive contamination could have been caused by an overturned lantern, it sounds like a pretty good explanation. (I will not judge how relevant it is to HN.)