No, fragments of the Tunguska object have not been found - or at least there is no real positive proof of that
The twittersphere, science news sites and mailinglists are abuzz with the story that fragments of the object that caused the famous 30 June 1908 Tunguska explosion have been found.
Most of them link to this post on the MIT Technology Review blog, which bases itself on this manuscript posted to Arxiv.org by a Russian named Andrei Zlobin.
To cut it short: it is highly unlikely the objects in question, which were reportedly retrieved from shoal sediments of the Khusmo river, are fragments of the Tunguska object. The "evidence" provided is wholly unsatisfactory. I am convinced the manuscript will not pass peer review (note that papers posted on Arxiv.org are manuscripts: the paper in question hasn't been accepted for publication by any scientific journal yet. And it shouldn't be, in my opinion).
In my opinion the pictured objects look like normal terrestrial iron hydroxide concretions, such as you can find in sandy soils with fluctuating water table and in bogs (and in river sediments that sample such environments). Morphologically they are quite typical for such concretions, especially specimens #3 and #1.
The shell-like character (e.g. #3) is characteristic, as such concretions often form as layers around a core of other material. So I see no reason at all to think these must instead be meteoritic.
In addition, the arxiv paper doesn't give any chemical analysis at all in support of the suggestion these are meteoritic particles. This while such an analysis is the least what you would expect for a claim like this.
The arxiv paper doesn't give any clear chronostratigraphical links between these particles and 1908 (and with this the Tunguska explosion) either. Why should this be particles from the 1908 explosion? What points to that particular origin for these particles? Do they come from sediments that are unambiguously dated to 1908? Zlobin gives no arguments at all.
In other words: this is highly dubious and for now a totally unbelievable story. It is a pitty that many science news websites, starting with the MIT Technology Review but also including Space.com are so uncritically disseminating this Arxiv.org manuscript.