Officials have halted U.S. spacewalks until they can test the strength of handrails that line the U.S. part of the International Space Station and are used to anchor the spacewalkers.

Space station managers said Wednesday they discovered some odd bubbling on the interior of some handrails that are still on the ground.

It isn't known whether any of the problematic handrails were installed on the station, but that's a chance officials weren't willing to take, said Kirk Shireman, deputy station program manager for NASA.

"Because we couldn't be sure, we were being conservative," he said.

Shireman said he doesn't believe any of the dozens of handrails at the station will have to be replaced.

The news comes at a time when Russian spacewalks also have been put on hold because four canisters needed to rid carbon dioxide from the air spacewalkers breathe can't be located on the station.

"We do lose things occasionally on board the space station," Shireman said. "There are little nooks and crannies and oh by the way, things don't stay where you put them. They float away."

A supply vehicle is scheduled to arrive next month with new canisters, which will allow Russian spacewalks.

Americans say they expect to have the handrail issue resolved well in advance of the next scheduled spacewalk after space shuttle Discovery's planned July launch.

Shireman said that if the metal's composition hasn't been compromised, astronauts could perform a spacewalk and attach their tethers to the fastener that holds the rail onto the station, rather than the rail itself.

The initial tests should be completed this week and the strength testing sometime next month.

The bubbling was discovered after the handrails were heat-treated during their manufacture, Shireman said.

"They got about 100 degrees hotter than they were supposed to get and ... it caused this change in the metal," he said. "You wouldn't want to hook one of these tethers to a piece of material you are not confident in."