The Columbia space shuttle was lost because damage to a seal or panel on its left wing allowed the super-hot gases of re-entry to get inside the vehicle frame and break it apart.

This is the Columbia Accident Investigation Board's (CIAB) "working scenario" - a best assessment of what happened to the orbiter based on the evidence gathered so far.

The scenario contains few surprises, keeping to the facts known about the flight - but stopping short of pulling them together into an explanation of the accident.

The space shuttle broke up over Texas on 1 February killing all seven crew members. It had been on a 16-day mission in space to conduct science experiments in micro-gravity.

The board notes that foam from the orbiter's external fuel tank struck the left wing 81 seconds after launch - but it does not at this stage say the impact doomed the shuttle.

"We're careful not to say the foam knocked a hole in the leading edge of the orbiter because we can't prove it," said retired admiral Harold Gehman, who heads the inquiry.

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BBC Science