A top Russian official acknowledged Thursday what many citizens already suspected — that terrorism was the most likely cause of two jetliners crashing minutes apart, a feeling reflected in a newspaper headline warning that "Russia now has a Sept. 11."
A day after officials stressed there were many possibilities besides terrorism, presidential envoy Vladimir Yakovlev told Russia's ITAR-Tass news agency that the main theory "all the same remains terrorism."
Yakovlev said the planes' flight recorders provide no clues to the disaster. He said both boxes had shut off abruptly without any indication of trouble, a sign U.S. aviation experts said was strong evidence of explosions.
Also, Transport Minister Igor Levitin confirmed Sibir airlines' report that its crew activated an emergency signal shortly before the plane disappeared from radar. Visiting the crash site, however, he said that details were slim because "no verbal confirmation from the crew was received" saying what the problem was.
Officials previously said there was no indication of trouble from a Volga-Aviaexpress airliner that also crashed late Tuesday, although people on the ground reported hearing a series of explosions.
CBS News has learned that investigators believe a woman suicide bomber may have been the cause of one of the crashes.
CBS News Correspondent Richard Roth says it's believed a woman was likely responsible -- wearing an explosive belt that could have passed through security undetected unless she was frisked. And women here rarely are.
Officials say a woman with a Chechen name is the only crash victim whose body has not been claimed, Roth reports, adding there is ''no information'' she was a terrorist.
Russian media also raised questions about a possible link between the crashes and an explosion a few hours earlier at a bus stop on a road leading to Domodedovo airport, where the two doomed planes took off. Without citing evidence, the reports suggested the blast, which wounded four people, might have been an effort to distract attention.
Suspicions of terrorism came after warnings from officials that separatists might plan attacks before an election this Sunday in Chechnya to replace the war-torn region's assassinated pro-Kremlin president. The rebels have made attacks in Moscow and other cities, hijacked planes outside Russia and allegedly staged suicide bombings.
"I am inclined to think that it is a terrorist act, because there are too many coincidences," said Ruben Suryaninov, an elderly retiree. "What needs to happen so that two planes going from the same airport would bang at the same moment?"
"It's too suspicious," agreed Natalia Kozhelupova, a physicist who was out on a national day of mourning for the 89 people killed in the crashes. Russia's tricolor flag flew at half-staff and television canceled entertainment programs.
Despite Yakovlev's statement about terrorism, the government was still officially investigating all possibilities — bombs, hijackers, mechanical failure, bad fuel and human error. Officials said no evidence had been found pointing to terrorism, and no one has claimed to have caused the crashes.
The government had hoped the jetliners' flight data recorders would shed some light, but Yakovlev told state-run First Channel that experts found the boxes in both planes shut off before indicating any problems.
Yakovlev, the president's envoy for southern Russia, where one of the planes crashed, said the recorders "turned off immediately" — an indication "that something happened very fast."
Bill Waldock, aviation safety professor at Embry-Riddle Aeronautical University in Arizona, said a sudden stoppage of a plane's two recorders indicates that its electrical system was cut. "An explosion could interrupt electrical power," he said, adding that it was extremely unlikely that another problem would cause four boxes in two planes to quit abruptly.
If something went wrong with a plane's mechanical or electrical systems, "more protracted data would show up," Waldock said. The cockpit voice recorder would pick up pilots' conversations as they dealt with the problem, while the flight data recorder would note such information as altitude, air speed, heading and vertical acceleration.
Peter Goelz, a former managing director of the National Transportation Safety Board, also said the abrupt shutoffs mostly likely point to explosions. But raised the possibility that the recorders weren't working properly.
"Given that Russian regional aviation has never been known for its maintenance standards, it would not surprise me that the FDRs and CVRs were not working correctly, if at all," Goelz said.
The planes — a Sibir Tu-154 with 46 aboard and a Volga-Aviaexpress Tu-134 with 43 people — disappeared from radar almost simultaneously around 11 p.m. Tuesday. The Tu-134 was headed to the southern city of Volgograd and the other plane to the Black Sea resort city of Sochi, where President Vladimir Putin was vacationing. They had taken off about 40 minutes apart.
A government commission appointed to investigate traveled Thursday to the site where the Tu-134 crashed, about 120 miles south of Moscow. Emergency crews had already completed their work there, but others continued to check the wreckage of the Tu-154 a few hundred miles south.
"There is still no clear-cut concept of what occurred, because the procedure of deciphering the data recorders will be conducted more than once," Levitin, the transport minister and head of the commission, was quoted as saying by ITAR-Tass.
Oleg Panteleyev, an independent aviation expert in Russia, said that just because no clear evidence of terrorism had been found, didn't mean that wasn't the cause.
Any other explanation "seems to be purely impossible," he told The Associated Press. "But then again, absolutely incredible things can happen in life."
Many ordinary Russians have ingrained doubts about the government's candor after the confused and contradictory reports on the sinking of the nuclear submarine Kursk in 2000 and the still-murky 2002 seizure of a Moscow theater by Chechen rebels.
"I never trust what the authorities are saying, but in this case, I don't know — it could have been an accident or a terrorist act," said Yevgeny Skepner, a 37-year-old computer programmer.
Still, Pavel Felgenhauer, an independent military analyst who is often critical of the government, said Moscow would have nothing to gain in covering up a terror attack.
"For the companies, the aviation industry, society and Russia as a whole, it would be better ... because otherwise it means that things are really bad here — we have bad planes that crash to the ground one after another," he said. "The fact that it is not being called a terrorist act, means they have no such evidence ... because hiding a terrorist act is impossible."
Panteleyev disagreed. "To miss such a major terrorist act for the security services means to acknowledge their impotence," he said.