US investigators said on January 20 that they are more convinced than ever of their original theory that the EgyptAir 990 was crashed deliberately.

The examination of the shattered Boeing 767, some 70 percent ofwhich was recovered from the ocean floor, has revealed no signs ofa mechanical failure that would have caused the plane to plummet 40 minutes into its 11-hour flight, according to government officials close to the investigation who asked not to be identified.

"Everything leads everyone to believe that the plane was mechanically sound and it was doing what it was supposed to, " one official said. There is just no "smoking gun" to indicate mechanical failure, he added.

Investigators have said that the cockpit voice recorder contained some utterance, perhaps a prayer, before the plane went into its fatal plunge. But Barry Schiff, a TWA pilot for 34 years who instructed trainees on the Boeing 767 and now serves as an aviation safety consultant, said the flight and radar data alone make it clear someone forced the aircraft down on October 31 last year off Massachusetts State's island of Nantucket, killing all 217 people aboard.

The US Federal Bureau of Investigation (FBI) has been involved from the start and has uncovered no evidence of terrorism or conspiracy.

Meanwhile, EgyptAir Chairman Mohamed Fahim Rayan said in Cairo that the plane's nearly sonic-speed descent was the result of "something happening" in the tail apparatus.

Walid Morad, chairman of the Egyptian Airline Pilots Association, said he would not reach any conclusions until US investigators, aided by Egyptian experts, issue a final report.