Moscow ? 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.”

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.

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.”