Mystery pieces of space debris which had shuttle mission controllers worried will not prevent a landing attempt Thursday, NASA said today.

A further three bits of dross were spotted during a close inspection today.

The original fragment had prompted fears something might have come unstuck from outside Atlantis during its eventful mission to the International Space Station.

The shuttle was due to land today, but jitters over the floating objects have now postponed it until Thursday.

NASA officials said their best guess was that the objects had drifted out of the cargo hold when it was opened, AP reports. Flight director Steve Stich said: "Typically, when we open the payload doors on the first day of flight, we will see objects. It's a little bit unusual to see objects maybe this late in the mission."

Engineers emphasised the inspection had revealed no problems with the heat shield.

Damage to the heat shield was behind the Columbia disaster in 2004. ®

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