The news of the discovery has come as an Islamist group reportedly claimed responsibility for the twin disaster when the two planes plunged to earth moments of each other on Tuesday after they took off from Moscow's Domodedovo airport.
"During the examination of the wreckage of the Tu-154 plane traces of explosives were found," a spokeswoman for the FSB security service said on Friday.
The explosive was identified as Hexogen - used in bombings in four Russian cities that prompted President Vladimir Putin's decision to launch the war in Chechnya nearly five years ago.
"The investigation process produced information which has allowed us to identify a number of people with possible links to the terrorist act that was committed on Tu-154," the spokeswoman said, adding that there was no fresh information about the other plane, a Tu-134.
Meanwhile, a group claimed it had hijacked the two planes to avenge the killing of Muslims in Chechnya and threatened more attacks, according to a statement posted on Friday on a website which usually carries such claims.
"Our mujahidin in the Islambuli Brigades were able to hijack two Russian planes and they were successful despite the obstacles that faced them at the beginning," it said.
An Islamist organisation has
allegedly claimed responsibility
"There were five (mujahidin) in each plane," said the Arabic-language statement, whose authenticity could not be verified.
However, critics of Russian policy in Chechnya have previously accused Moscow of blaming Chechen separatists for atrocities in order to justify crackdowns and tighter security measures.
The news agencies ITAR-TASS and Interfax quoting investigators said one of the passengers aboard the flight to Sochi was a woman from Chechnya whose remains have yet to be claimed by friends or relatives.
Head of the interior ministry for Chechnya, Akhmad Dakayev, told Interfax that another woman who was registered in Grozny, the rebel capital, was on board the second plane.
"We have received instructions to find out the identities of the two Chechen women"
Chechen interior ministry
"We have received instructions to find out the identities of the two Chechen women," Interfax quoted Dakayev as saying.
The Tu-154, bound for Sochi on the Black Sea, crashed near the southern city of Rostov-on-Don on Tuesday, moments after a Tu-134 flying to Volgograd crashed near the town of Tula, south of Moscow.