An internal NASA probe and an external committee of experts are already preparing the ground to find out exactly what caused Columbia to break apart over Texas.

The two teams will work in tandem with the help of hundreds of scientists and engineers to gather debris, analyse data and ultimately determine the cause of the crash. David Whittle, an administrator at NASA's Johnson Space Center in Texas, will head the internal probe, while the external investigation is being led by retired navy admiral Harold Gehman, who co-chaired the independent commission that looked into the terrorist attack on the USS Cole in 2000.

The swift decision to set up an external probe contrasts with the agency's handling of the 1986 Challenger disaster. NASA's silence in the first few days after that accident led some to accuse the agency of withholding information.

This time around, NASA quickly convened not just an outside review, but frequent press briefings on the accident. “This is going to be the most open accident investigation people have experienced,” pledges Michael Kostelnik, a senior administrator on the shuttle programme.

An early focus for the two investigations is the ceramic tiles on the shuttle's underside, which protect the heat-sensitive aluminium airframe during reentry into the atmosphere. Mark Lewis, a professor of aerospace engineering at the University of Maryland who specializes in re-entry physics, says: “I think it's conceivable that the loss of one tile in certain locations would be catastrophic.”

Without ruling out other possible causes, investigators are looking at the possibility that the left wing of Columbia was damaged when debris from the shuttle's main fuel tank fell on it just after take-off. Programme manager Ron Dittemore says that a similar incident in 1992 left a several-inch-long gash in heat tiles on Columbia's wing, but it was concluded that the incident would not have endangered the shuttle.

Albert Wheelon, a physicist who served on the presidential commission that investigated the Challenger accident, predicts that investigators will soon move on from technical causes to possible management failures. “The first problem is to find out what went haywire,” he says. “Then they must determine if there were hints of this beforehand, or if it was a bolt out of the blue.”