The Russian Transport Ministry said that investigators have begun to decipher the flight data recorders of the military plane that came from Warsaw.
The recorders contain crew conversations and flight data, which is essential to determine the cause of the Tu-154's crash, The Miami Herald reports.
All 97 people on board were killed when the plane crashed in thick fog while approaching Smolensk airport.
Meanwhile, a week of national mourning has begun in Poland, and a two-minute silence was held at noon local time on Sunday.
The Polish Foreign Ministry confirmed that along with the President and his wife, others on board included Polish Deputy Foreign Minister Andrzej Kremer, Army Chief Franciszek Gagor and National Bank President Slawomir Skrzypek.
Some 88 of the dead were members of a Polish state delegation, who were scheduled to attend events marking the 70th anniversary of the massacre in Katyn forest of 22,000 Polish officers by Soviet secret police.
Polish Prime Minister Donald Tusk said the crash was the most tragic event of the country's post-World War II history.
Russian President Dmitry Medvedev has appointed Prime Minister Vladimir Putin as the head of a commission to investigate the crash. (ANI)