CAPE CANAVERAL, Fla. -- Space shuttle Columbia apparently disintegrated in flames over Texas minutes before it was to land Saturday in Florida. TV video showed what appeared to be falling debris, as NASA declared an emergency and sent search teams to the Dallas-Fort Worth area.\nIn north Texas, several residents reported hearing "a big bang" at about 9 a.m., the same time all radio and data communication with the shuttle and its crew of seven was lost.\nOfficials in Washington said that there was no immediate indication of terrorism, and that President Bush was informed and awaiting more information from NASA.\nJust over an hour after the shuttle had been expected to land, officials at Kennedy Space Center announced over loud speakers that a statement on the fate of the shuttle would be issued shortly. NASA warned people on the ground in Texas to stay away from any fallen debris.\nIt was the 113th flight in the shuttle program's 22 years and the 28th flight for Columbia, NASA oldest shuttle. Six Americans and Israel's first astronaut were on board.\nInside Mission Control, flight controllers hovered in front of their computers, staring at the screens after contact was lost. The wives, husbands and children of the astronauts who had been waiting at the landing strip were gathered together by NASA and taken to a secluded place.\n"A contingency for the space shuttle has been declared," Mission Control somberly repeated over and over as no word or any data came from Columbia.\nIn 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.\nShortly after Columbia lifted off Jan. 16, a piece of insulating foam on its external fuel tank came off and was believed to have hit 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.\nColumbia had been aiming for a landing at 9:16 a.m. Saturday.\nIt 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 all contact and tracking data.\nGary 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."\n"The barn started shaking and we ran out and started looking around," said Benjamin Laster of Kemp, Texas. "I saw a puff of vapor and smoke and saw big chunk of material fall."\nTelevision footage showed a bright light followed by smoke plumes streaking diagonally through the sky. Debris appeared to break off into separate balls of light as it continued downward.\nSecurity had been extraordinarily tight for Columbia's 16-day scientific research mission because of the presence of Ilan Ramon, the first Israeli astronaut.\nRamon, 48, a colonel in Israel's air force and former fighter pilot, had survived two wars. He 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.\nA senior U.S. official, speaking on condition of anonymity, said Saturday there was no threat made against the flight and that the shuttle was out of range of a surface-to-air missile.\n"The government of Israel and the people of Israel are praying together with the entire world for the safety of the astronauts on the shuttle Columbia," Prime Minister Ariel Sharon's office said in a statement.\nColumbia's crew had completed 80-plus scientific research experiments during their time in orbit.\nOnly two of the seven astronauts had flown in space before, the shuttle's commander, Rick Husband, and Kalpana Chawla. The other five were rookies: pilot William McCool and Michael Anderson, David Brown, Laurel Clark and Ramon.\nJust in the past week, NASA observed the anniversary of its only two other space tragedies, the Challenger explosion, which killed all seven astronauts on board, and the Apollo spacecraft fire that killed three on Jan. 27, 1967.