Wreckage of a Tu-154 airliner is seen at a crash site near Gluboky in the Rostov region some 600 miles south of Moscow, Tuesday, Aug. 25, 2004.
(Sergei Venyavsky/AP Photo)
Traces of explosives found in one of two downed Tupolev planes match explosives used in the 1999 bombing attacks of Moscow apartments by Chechen separatists, according to two U.S. government sources.
These sources told ABC News that according to reports received by U.S. investigators in Moscow, suicide attacks are now being viewed as the most probable cause for the destruction of the planes.
U.S. government sources confirm that investigators in Russia have a "very high degree of certainty" that "martyrs," or suicide bombers, were involved in the attack.
The highly sophisticated explosive RDX — also known as cyclonite or hexogen — is a military explosive with very limited commerical use.
In what Russian sources are calling "Russia's 9/11," Sibir Airlines' Tu-154 and Tu-134 jets went down within 20 minutes of each other after taking off from the same Moscow airport Tuesday night.
Unidentified Chechen Women on Board
Although Russia's Federal Security Service, known as the FSB, has been cautious about calling Tuesday's attacks the work of terrorists, Russian media reports have indicated otherwise.
The ITAR-TASS news agency reported today that, according to air traffic controller sources, the Tu-154 signaled three times that it had been hijacked before it crashed.
The Russian Strana.ru news service reported that there was at least one Chechen woman aboard each of the planes, and that no one has come to identify or claim their remains.
Some of the remains of the Chechen woman on the Tu-154 were found in the plane's rear toilet, according to the report.
Chechen female bombers — known as "black widows" in Russia — have recently begun participating in major militant operations in Russia.
Chechnya's 'black widows" first shot into the limelight during the deadly October 2002 Moscow theater siege and have been responsible for several attacks since, according to Russian officials.
Tuesday's aviation disaster came days ahead of crucial Chechen presidential elections set for this weekend, and Russian security forces were on alert for terrorist attacks.
Web ‘Statement’ Claims Responsibility
The new findings follow a purported Web statement by an Islamist group taking responsibility for Tuesday's "operation."
In the statement, a group called the Islambouli Brigades said it had five mujahedeen, or holy fighters, on board each aircraft. It warned this act would be followed by others "until the killings of our Muslim brothers in Chechnya cease."
Russian security officials have refused to confirm or comment on the statement.
Although it is not known if the Islambouli Brigades has any link to al Qaeda, a group with a similar name claimed responsibility for last month's attempt to assassinate a senior Pakistani official.