MOSCOW - A top Russian official said today that flight recorders failed to provide reliable information about what brought down two jetliners nearly simultaneously, killing 89 people, but that terrorism remained a leading possibility.

Vladimir Yakovlev, the Russian president's envoy for the southern region, where one of the planes crashed, said despite the lack of information, the main theory about the catastrophe "all the same remains terrorism," the ITAR-Tass news agency said.

The failure of the recorders to provide significant information could increase what appears to be rising suspicion among Russians that the crashes were terrorist acts.

The suspicions are bolstered by the fact the crashes took place just five days before a Kremlin-called election in warring Chechnya, whose separatist rebels have been blamed in a series of suicide bombings in recent years.

Yakovlev told First Channel television that the recorders "turned off immediately ... this is probably the main affirmation that something happened very fast."

Officials have said several possibilities were being investigated as the cause of Tuesday's crashes, including inferior fuel and human error. They had hoped the planes' data recorders would yield clues.

But Yakovlev said the recorders "had gone out of service already before the fall of the airliners," ITAR-Tass said.

A government commission appointed to investigate traveled today to the crash site about 120 miles south of Moscow, where a Tu-134 with 43 people aboard went down. Workers ended their search work there, but continued to comb the wreckage of a Tu-154 that crashed in southern Russia, killing 46 passengers and crew.

Despite the lack of an official conclusion on the causes, the crashes nonetheless raised serious concerns about security at Russian airports. President Vladimir Putin on Wednesday ordered the government to draft legislation to turn over responsibility for airport security to the Interior Ministry, which runs both the police and paramilitary forces, according to news reports.

The planes disappeared from radar around 11 p.m. local time Tuesday. The Tu-134 was headed to the southern city of Volgograd. The other plane was headed to the Black Sea resort city of Sochi.

Both had taken off from the single terminal at Moscow's newly renovated Domodedovo airport, the Sibir airlines' Tu-154 around 9:35 p.m. and the smaller Tu-134 about 40 minutes later.

Sibir said it was notified that its jet had activated an emergency signal shortly before disappearing from radar screens. Officials said there were no indications of trouble with the other plane, but witnesses on the ground reported hearing a series of explosions.

But there was skepticism that technical failure or human error could bring down two planes at almost the same time hundreds of miles apart. "That's pretty far out there on the chance bar," said Bob Francis, former vice chairman of the U.S. National Transportation Safety Board.

Jim Burin of the U.S.-based Flight Safety Foundation said that although bad fuel could cause an airplane's engines to fail, the problems likely would be noticed and reported by the crew well in advance as the engines began to labor or misfire.

He added that initial reports from the crash scenes indicated that one plane's wreckage was spread out more widely than would usually be the case in a crash that was not preceded by an explosion.