Amateurbeelden van de verongelukte Columbia.
SHUTTLE CREW
Commander Rick Husband, US
Pilot William McCool, US
Kalpana Chawla, US
Laurel Clark, US
Ilan Ramon, Israel
David Brown, US
Michael Anderson, US
The US space shuttle Columbia has broken up soon after re-entering the Earth's atmosphere, killing all seven crew on board. The space agency Nasa lost contact with the craft about 15 minutes before it was due to land at the Kennedy Space Center in Florida.
Contact was lost over Texas
Nasa administrator Sean O'Keefe told a news conference it was a "tragic day" for the Nasa family. He paid tribute to the dead crew as "extraordinary" people, and said everything would be done to help their families through this period. Mr O'Keefe said there was no indication that the disaster had been caused by anything or anyone on the ground.
Hundreds of state troopers, police and rescue workers are searching large areas of rugged terrain in eastern Texas for debris from the shuttle.
President Bush has been briefed about the disaster and is expected to make a statement shortly.
Heightened security had surrounded Columbia's latest mission because of the presence of Colonel Ramon, the first Israeli in space. In Israel, officials described events as a national tragedy.
Columbia, which had been due to land at 0916 (1416GMT) was returning from a 16-day mission orbiting the Earth and had just begun its re-entry procedure when contact was lost at about 0900 local. Nasa said the shuttle was about 200,000 feet up and travelling at 12,500 mph (20,000 kph) at the time.
Texas public safety department spokesman Clive Kennelly said there were more than 2,000 debris fields, scattered from the small town of Nacogdoches about 170 miles (290 km) south-east of Dallas, to the Louisiana border.
'Hazardous'
In 42 years of human space flight, Nasa has never lost a space crew during landing. In 1986, the space shuttle Challenger exploded shortly after lift-off with the loss of all seven crew on board.
Columbia, which first flew in 1981, was the oldest craft in Nasa's space shuttle programme.
Nasa has assigned a former astronaut to the family of each crew-member to provide support. "They have been with each family since the mission began and are trying to help them cope with this terrible tragedy," a Nasa official told the BBC.
'Catastrophic failure'
Former Nasa chief historian Roger Launius told BBC News that it looked like this was a "catastrophic failure."
The BBC's Leo Enright says that one immediate concern is the fate of the International Space Station.
Three crewmen are currently living and working aboard the station, and the space shuttle is a vital link providing them with supplies. Europe, Japan, Canada and Russia have all invested heavily in this enterprise, which had come to rely more and more on the Americans' space shuttle fleet.
Our correspondent says all future plans must now be reviewed, and experts must decide whether the station can remain operational or whether it should be mothballed.