CAPE CANAVERAL, Fla. (Feb. 1) - Space shuttle Columbia apparently disintegrated in flames over Texas on Saturday minutes before it was to land in Florida. TV video showed what appeared to be falling debris, as NASA declared an emergency and warned residents to beware of falling objects.

Six Americans and Israel's first astronaut were on board.

In north Texas, people reported hearing ''a big bang'' at about 9 a.m., the same time all radio and data communication with the shuttle was lost.

Television stations showed what appeared to be flaming debris falling through the sky, and NASA warned Texas residents to beware of any falling objects. NASA also announced that search and rescue teams were being mobilized in the Dallas and Fort Worth areas.

Inside Mission Control, flight controllers hovered in front of their computers, staring at the screens. The wives, husbands and children of the astronauts who had been waiting at the landing strip were gathered together by NASA and taken to secluded place.

''A contingency for the space shuttle has been declared,'' Mission Control repeated over and over as no word or any data came from Columbia.

In 42 years of U.S. human space flight, there had never been an accident during the descent to Earth or landing. On Jan. 28, 1986, space shuttle Challenger exploded shortly after liftoff.

On Jan. 16, shortly after Columbia lifted off, a piece of insulating foam on its external fuel tank came off and was believed to have struck the left wing of the shuttle. Leroy Cain, the lead flight director in Mission Control, assured reporters Friday that engineers had concluded that any damage to the wing was considered minor and posed no safety hazard.

Columbia had been aiming for a landing at 9:16 a.m. Saturday.

It was at an altitude of 207,000 feet over north-central Texas at a 9 a.m., traveling at 12,500 mph when Mission Control lost contact and tracking data.

Gary Hunziker in Plano said he saw the shuttle flying overhead. ''I could see two bright objects flying off each side of it,'' he told The Associated Press. ''I just assumed they were chase jets.''

''I was getting ready to go out and I heard a big bang and the windows shook in the house,'' Ferolito told The AP. ''I thought it was a sonic boom.''

Security had been tight for the 16-day scientific research mission because of the presence of Ilan Ramon, the first Israeli astronaut.

Ramon, a colonel in Israel's air force and former fighter pilot, became the first man from his country to fly in space, and his presence resulted in an increase in security, not only for Columbia's launch, but also for its planned landing. Space agency officials feared his presence might make the shuttle more of a terrorist target.

Israeli Prime Minister Ariel Sharon's office said it had no immediate comment.

Columbia's crew had completed 80-plus scientific research experiments during their time in orbit.

Just in the last week, NASA observed the anniversary of its only two other space tragedies, the Challenger explosion, which killed all seven astronauts on board, and Apollo space craft fire that killed three on Jan. 27, 1967.

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