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.
Traces of the same explosive were found on the Tu-154 jetliner that crashed near Rostov in southwestern Russia, officials said Friday. The two planes took off from the same terminal at Moscow's Domodedovo Airport and went off radar screens within minutes of each other hundreds of miles apart on different routes. All 90 people on board died.
The discoveries pointed to terrorism as the cause of both crashes -- suggesting that militants had succeeded in getting bombs past airport security to attack Russia's civil aviation system, a vital industry in this vast nation.
Transport Minister Igor Levitin announced that police would now help screen passengers and bags -- currently the responsibility of the airports.
Additionally, the ministry will require airlines to print full passport details from passengers on tickets, the ITAR-Tass news agency reported. Russian citizens have separate passports for internal and foreign travel.
The Israeli air travel systemIgnatchenko said the FSB -- a successor to the Soviet-era KGB -- had been directed by President Vladimir Putin to study other countries' practices to improve air security.
"International experience in fighting terrorism on air transport is being studied, including proposals to use the Israeli system ... which today is recognized as the most effective in the world," Ignatchenko said.
Hexogen was used in a series of apartment bombings that killed more than 300 people in Russia and were blamed on separatist rebels from Russia's Chechnya region. Russian officials have warned of more rebel attacks ahead of today's election to choose a new regional president to replace Akhmad Kadyrov, killed in a bomb attack May 9.
The Russian government has portrayed the election -- which a Kremlin-supported police official is expected to win -- as a sign that peace is returning to a region ravaged by a decade of fighting between Russian troops and insurgents. Russian soldiers occupying Chechnya are still regularly killed and wounded by small-scale attacks and bombings.
Speculation that rebels were behind an attack on the planes grew with news that authorities were looking into the backgrounds of two female passengers who boarded under Chechen names, one on each plane.
Both women had booked tickets on the flights at the last minute and were the only victims whose relatives did not contact authorities after news of the crashes, officials said. One of the women gave only her surname and first initial in booking the ticket, according to reports.
A Web site statement, posted Friday and signed the "Islambouli Brigades," claimed responsibility for the crashes, warning that they were in support of the Chechen rebels and marked just the first in a series of planned operations. The claim's veracity could not be confirmed.
Friday's claim came from a purported group called "the Islambouli Brigades of al-Qaida," which claimed responsibility for last month's attempt to assassinate Pakistan's prime minister-designate.
Russia claims that the Chechen rebels have been joined by hundreds of foreign Islamic fighters, many of them al-Qaida or with links to the terrorist group led by Osama bin Laden.