Another "source/expert" told "
Kommersant" that bomb was planted under seat in the right rear last row. It makes hole 0.8 x 1 m and cut signal cables to FDR. So either he has some inside info or read pprune/aviaforum.
Also there is another leak, now LifeNews: examination was carried on 34 bodies of passengers occupying rows 32-38, which bears explosion marks and also traces of TNT. No definite place of explosive device determined, versions are from rear cargo hold to under a seat to on the body of suicide bomber to upper cargo compartment.
Also "experts" claims that blast was directed from rear to front, separating tail section, so bodies of the front passengers and crew doesn't' bear explosion marks.