Cape Canaveral, Fla. ? Workers may have accidentally cut or crushed the section of foam that broke off Discovery’s fuel tank during its launch two months ago – a mishap that threatened the safety of the astronauts and grounded the shuttle fleet.

That is the leading theory for the cause behind the disturbing loss of foam insulation that cast a cloud over NASA’s return to space, said Wayne Hale, the newly appointed manager of the space shuttle program.

In a wide-ranging interview with The Associated Press on Tuesday, Hale said the shuttle will not fly again until the foam insulation problem is resolved – no sooner than spring.

He also said repair work has been set back because of hurricanes Katrina and Rita. The storms dealt “a severe blow” to resuming shuttle flights and caused NASA to lose three months of work, he said.

“We’re working a spring kind of launch date, but we haven’t established one,” he said. May is the earliest, most likely target.

To NASA’s horror, a 1-pound, 3-foot chunk of insulating foam peeled away from Discovery’s external fuel tank during liftoff in late July. It was the same kind of problem that doomed Columbia in 2003, and occurred despite 2 1/2 years of improvements and assurances that this was the safest tank ever built.

What probably happened is that during work on the tank at Michoud, technicians damaged the section while working on nearby areas, Hale said. “This foam, which normally is not touched after it’s applied, clearly was touched,” he said.

Workers using knives to remove nearby foam may have made small cuts in the section that tore away, allowing air to condense in the crevices against the tank, Hale said. Another possibility, he said, is that workers leaned against the piece of foam that broke off.

Engineers have more work to do before confirming any of this, the shuttle manager said. A fuel tank that finally arrived at Michoud this week from Cape Canaveral – a trip delayed by the hurricanes – will be dissected for evidence of damage. The earliest that a modified tank could be returned to Cape Canaveral is February, making a spring launch a possibility, Hale said.