Where is enormous quantity of extraterrestial substance, which the hypothetic Tunguska body was to loose before its explosion? Indeed, according to practically all
calculations, the hypothetic Tunguska spacebody lost a significant
(probably even dominated) portion of its mass before it reached the
explosion altitude of 5-8 km. In other words, at least, a hundred
thousands tonns of extraterrestrial substance (from large fragments to
dust) must be deposited along the lower part of Tunguska spacebody
trajectory. Despite many years of careful search nothing was
discovered... By the way, a couple years ago application of just one of
the many Tunguska substance search's methods allowed easily find small
fragments of a meteorite (with initial mass of several tonns, probably),
which disintegrated over another place in Siberia in 1904.