FSB spokesman Sergei Ignatchenko also said that the investigators are close to identifying the attackers of Tu-154 plane of the Sibir Airlines which crashed in Rostov region.

"In the process of operational investigation activities information has been received on the basis of which attackers of Tu-154 can be identified," Ignatchenko was quoted as saying by ITAR-TASS.

Although the traces of explosives were not yet found in the wreckage of another plane which crashed on the fateful night 200 kms from Moscow after taking off from the same airport here, the search teams have not found the fragments of 44th passenger Amanita Nagayeva, he said.

According to Radio Mayak, 30-year-old Amanta Nagayeva was the resident of Chechnya capital Grozny and had bought ticket on Moscow-Volgograd flight an hour before departure. No queries from her relatives have been received, the radio noted. Earlier, Sibir Airlines had also said that nobody has enquired about the fate of one of the woman F Jihirkhanova, who was travelling on Moscow-Sochi flight on board Tu-154 plane.

A Tupolev Tu-134 plane with 44 people on board, including 8 crew, crashed in the Tula region about 200 km south of Moscow on Wednesday. Around the same time, a  Tu-154 of Siberian Airlines with 46 people on board disappeared from the radars after sending a distress signal suggesting it had been hijacked. The two aircraft had taken off from  Moscow's Demodedovo airport within three minutes of each other.