The internal inquiry will be shadowed by an external board made up of experts from the Air Force and Navy - which had five of the seven crew members - and officials from the Transportation Department and other federal agencies.

First flight: 1981 Orbiting speed: 17,500 mph Landing weight: 105 tonnes Crew (for this mission):7

Columbia: Space pioneer

Within minutes of Columbia's loss, computer records were impounded together with documentation relating to the pre-flight preparation of the orbiter.

This information could be crucial to discovering what went wrong - as will the widely scattered debris. Collection teams are being put in place to gather up the fragments that came down over eastern Texas.

There were data and voice recorders on board the shuttle but it is thought these devices would not have survived the fireball that engulfed the vehicle or the impact into the ground.

Last transmission

None of the three remaining shuttles in the fleet will fly until the inquiry boards are satisfied they know the cause of the disaster.

Nasa officials at the Johnson Space Center in Houston said there had been a loss of key data transmissions from the left side of the orbiter just before contact was lost.

Concerns about insulation foam on lift-off

At 0853 EST (1353 GMT) sensors at the trailing edge of the left wing shut down. Their loss was followed by other temperature sensors in a more forward position.

"But the vehicle was flying with no problems at that time," Nasa's chief flight director Milt Heflin told reporters.

"When things like this happen, when a crew gets an alert - you acknowledge it, they recognise they've seen it.

"As far as I know, that was the last transmission from the crew. They were acknowledging, we believe, they'd seen the indication. Then we lost all vehicle data," he said.

Concern has been raised about a piece of insulating foam that was seen to hit Columbia's left wing on launch on 16 January. The foam had come away from the orbiter's external fuel tank.

Peak heating

But Ron Dittemore, the shuttle programme manager, urged people not to jump to conclusions.

"The impact was on the left wing and all the [sensor problems] were on the left wing. We can't discount that there might be a connection but we can't rush to judgement on it because there are a lot of things in this business that look like the smoking gun but turn out not to be."

When contact was lost with Columbia it was at an altitude of 207,135 feet (63,134 metres) and travelling at about Mach 18 (18 times the speed of sound). It would have been banking to the left to try to reduce its speed prior to landing.

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The temperature on the leading edge of the wings would have been about 1,650 Celsius (3,000 Fahrenheit) - peak re-entry heating.

"We're going to fix this problem and we going to launch shuttles again," Mr Dittemore said.

Of more immediate concern will be the status of the current resident crew on the International Space Station. The Russians are due to send up a cargo ship to the ISS with new supplies on Sunday.

Nasa has reviewed the contents of the delivery to ensure the station can continue to function without a visit from a shuttle for some months.

"We have enough consumables, supplies, for the crew to go through to the latter part of June without having the shuttle visit," Mr Dittemore added.