Up to six pieces of debris fell off Discovery: NASA

Up to six pieces of debris that could be foam insulation fell off Discovery's troublesome external fuel tank minutes after liftoff Tuesday, a top NASA official said.

Officials cautioned, however, that it was too soon to know whether the debris struck Discovery and that the pieces came off later than would normally endanger the shuttle.

Columbia's demise in February 2003 was caused by foam insulation that peeled off 70 seconds after liftoff and struck its heat shield.

"About two minutes and 47 seconds give or take (after the Discovery launch), we saw three perhaps four pieces come off (the fuel tank)," said shuttle program manager Wayne Hale, adding that it was unclear whether it was foam or "something else."

"We also saw another piece or two come off at about four minutes 50 seconds," he told reporters at the Kennedy Space Center.

He cautioned, however, that it was "very raw, preliminary data" and would have another report later Tuesday.

But Hale said the debris came off the fuel tank later than officials fear it could damage the shuttle's heat shield.