Washington: In a first ever public admission, investigators probing the Columbia space disaster on June 25 blamed the breakaway foam as "the most probable cause" for the disintegration of the spacecraft that killed Kalpana Chawla and six other astronauts.

"It is a pretty compelling story that in fact the foam is the most probable cause of the shuttle accident, Roger Tetrault, member of the Columbia Accident Investigation Board said after examining closely several pieces of the shuttle wreckage.

Tetrault beleives that the fatal breach in the shuttle's left wing, which was struck by insulation foam just 82 seconds after lift-off on January 16, 2003 resulted in the spacecraft's disintegration on February 1.

The damaged portion was located at or near panel number eight on the left wing, he said.

The engineering analysis, as well as the shuttle wreckage pinpoints to that location, he said.

The most compelling evidence for the foam theory was the launch video, which clearly shows the insulation foam breaking away from the external fuel tank and hitting the panels on the left wing.

The Board is expected to complete the report by July end and the investigators are struggling with how best to word it.

"The board is trying to craft words which will force NASA (National Aeronautics and Space Administration) to do something," Board chairman Harold Gehman said.

The Board is slated to carry out a final foam-impact simulation test early next month to re-create the conditions of an impact to panel eight of Columbia's left wing.

PTI