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1 News: Michelle Downey-Simpson reports on the discovery of traces of explosives in the wreckage of one of the two planes that crashed within minutes of each other in Russia on Tuesday
Russia's security service has said at least one of the two plane crashes that killed almost 90 people on Tuesday was the result of a terrorist attack.
The announcement followed a claim by an Islamic group that supports Chechen rebels saying it was responsible for both crashes.
A spokesman for the FSB security service said investigators had discovered traces of the explosive Hexogen, which is used by Chechens, in the wreckage of one of the two planes.
He refused to comment on the Islamic group's claim, which was made on an Internet website.
Hexogen was used in a series of apartment building blasts that killed around 200 people in Russia in 1999.
