Space shuttle Columbia broke apart in flames 200,000 feet over Texas on Saturday, killing all seven astronauts just minutes before they were to glide to a landing in Florida.
"Columbia is lost; there are no survivors," President Bush announced to a stunned nation.
NASA lost contact with the shuttle at 9 a.m. EST, 16 minutes before it had been scheduled to land. Bill Readdy, NASA associate administrator for space flight, said it was too early to speculate about a cause. A senior U.S. official said there was no indication of terrorism.
The first indication of a potential problem occurred minutes before 9 a.m. when there was a loss of temperature sensors on left wing, said Ron Dittemore, the shuttle program manager. During Columbia's liftoff, a piece of insulating foam from the fuel tank was believed to have hit that wing.
Dittemore said the loss of the sensors on the left wing was followed seconds later by several other problems, including a loss of tire pressure and indications of excessive structural heating.
"Our thoughts and our prayers go out to the families of Rick and Willie and Davie and Kalpana, Michael and Larel and Ilan. True heroes," he said.
He said there was a hold on space flights and that an investigative board outside NASA would help determine the root cause of the problem, but he said it was too early to say what long-term impact the tragedy would have on the shuttle program.
The crew aboard the international space station will have enough supplies to last through the end of June, Dittemoore said. The Russian Space Agency said a Sunday launch of a Progress cargo ship to the station would go forward as planned.