Commander of Lithuania's Armed Forces Major General Valdas Tutkus said it could take several weeks to recover the remnants of the plane that had crashed in Lithuania Thursday.
The general said some parts of the plane are buried 5-6 meters deep in the ground.
According to unconfirmed reports, experts from the investigation team recovered a "black box" from the plane Saturday in the presence of Russian observers and delivered it to Vilnius.
Earlier, the Lithuanian defense ministry officials and head of the Russian observer's team Major General Sergey Bainetov had confirmed that the Su-27 fighter had four air-to-air missiles on board.
According to Bainetov, missiles did not explode during the crash and are buried in the wreckage.
Gediminas Kirkilas said the pilot could have released the missiles before the plane hit the ground.
He also said Russian pilot Valery Troyanov had been constantly changing the details of his witness account and they differed significantly from the Russian official version of the accident.