Houston ? Columbia accident investigators said Tuesday they are close to zeroing in on where a hole opened up in the spaceship’s left wing and strongly suspect the fatal blow was caused by a chunk of flyaway foam at liftoff.

“I feel that we’re probably within 30 inches of where the actual breach occurred,” said Roger Tetrault, a member of the Columbia Accident Investigation Board. “We’re closing in.”

A fragment of a panel or seal along the vulnerable leading edge of Columbia’s left wing is almost certainly what was missing when Columbia descended through the atmosphere three months ago this week, the board said. This missing mystery object floated away two days into the doomed flight, unnoticed by the crew or ground controllers.