Investigators find explosive in one of the crashed Russian jets

Traces of explosives have been found in the &to=http://english.pravda.ru/accidents/21/97/384/13891_crash.html' target=_blank>wreckage of one of two Russian airliners that crashed nearly simultaneously earlier this week, the Federal Security Service said Friday, a day after a top official acknowledged that terrorism was most likely behind the crashes.

A spokesman for the security agency, Nikolai Zakharov, said on Russian television that preliminary analysis shows traces of "hexogen" were found in the shattered Tu-154 jetliner that crashed in southern Russia.

Hexogen is the explosive that officials said was used in the 1999 apartment bombings that killed some 300 people in Russia and were blamed on Chechen separatists.

Another Federal Security Agency spokesman, Sergei Ignatchenko, said authorities were trying "to determine the circle of people who may have been involved in an act of terrorism aboard the Tu-154," according to the Interfax news agency.

Investigators were searching for information about &to=http://english.pravda.ru/accidents/ 21/96/382/10473_chechen.html' target=_blank>two women with Chechen surnames who were on the planes' passenger lists, Russian news agencies reported Friday. The women were reportedly the only passengers about whom relatives have not inquired.

Chechen rebels and their supporters have been blamed for a series of suicide bombings and other attacks in Russia over the past several years, including last year's suicide bombings of an outdoor rock concert in Moscow and another outside a hotel near Red Square, informs Associated Press.

According to BBC the Tu-134 and Tu-154 crashed within minutes of each other over southern Russia, coming down at about 800km (500 miles) apart.