text: Russia Finds Trace Explosives on 2nd Plane MOSCOW - Russian investigators found explosive residue on the wreckage of the second of two airliners that crashed minutes apart, a security spokesman said Saturday, adding to evidence that terrorists breached security at one of the country's most up-to-date airports.    The high explosive hexogen was found on the Tu-134 airliner that went down Tuesday south of Moscow, said Sergei Ignatchenko, spokesman for the Federal Security Service, or FSB, Russia's domestic security agency...