An astronaut was left helplessly watching her tool bag and everything inside it float away after accidentally dropping it in space.

Thought to be one of the biggest items ever to be lost by a spacewalker, Heidemarie Stefanyshyn-Piper dropped the tools while trying to clean and loosen a joint at the International Space Station.

She said her grease gun exploded, getting the dark gray grease all over a camera and her gloves.

While she was wiping everything off, the white, backpack-size bag slipped out of her grip, and she lost all her tools.

"Oh, great," she is heard mumbling.

Stefanyshyn-Piper and her fellow spacewalker, Stephen Bowen, then finished their tasks in almost seven hours by sharing tools.

Flight controllers were assessing the impact the lost bag would have on the next three planned spacewalks.

The astronauts may be asked to keep sharing tools or use caulking-style guns intended for repairs to the shuttle's thermal shielding.

By late Tuesday, the bag was already more than two miles (3.2km) in front of the shuttle-station complex.

Nasa was not sure how the bag got loose as it should have been tethered to a larger equipment bag.

John Ray, the lead spacewalk officer at Mission Control said it was merely proof of the difficulties the astronauts face with "one small mistake" causing so much drama.

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