HOUSTON (AP) — Flight controllers were revamping plans today for the remaining spacewalks planned during space shuttle Endeavour’s visit to the international space station, after a crucial tool bag floated out to space.

The briefcase-sized tool bag drifted away from astronaut Heidemarie Stefanyshyn-Piper on Tuesday as she cleaned and lubed a gummed-up joint on a wing of solar panels on the space station. She and fellow astronaut Stephen Bowen were midway through the first of four spacewalks planned for the mission. The tool bag was one of the largest items ever lost by a spacewalker.

As Stefanyshyn-Piper cleaned up a large gob of grease that seeped from a gun used to lubricate the joint, the tool case somehow became untethered from a larger bag and floated away along with a pair of grease guns.

“What it boils down to is all it takes is one small mistake for a tether not to be hooked up quite correctly or to slip off, and that’s what happened here,” said lead spacewalk officer John Ray.

Stefanyshyn-Piper and Bowen finished the spacewalk in almost seven hours by sharing tools from Bowen’s bag.