Space debris threatened the seven astronauts aboard the International Space Station, forcing them to seek shelter in their docked capsules.
The US space command said it was tracking a debris field in orbit that was allegedly the result of a satellite crash.
The astronauts retired to their docked capsules early Monday after learning of the threat at the last minute.
Mission Control instructed them to later close the hatches between the compartments of the space station for safety reasons.
The space command said in a statement: “We are actively working to characterize the debris field and will continue to ensure that all space travel nations have the information they need to maneuver satellites in the event of an impact.”
NASA officials made no comment.
The Russian space agency said on Twitter that the astronauts were ordered to their docked capsules earlier in the day in case they need to flee quickly.
The crew later “conducted routine operations,” the agency noted.
The commander of the space station, the Russian Anton Shkaplerov, said on Twitter: “Friends, everything is regular with us!”
The cloud of debris appeared to pose a threat in any passing orbit, and the crew later paused their scientific research to re-establish safety precautions.
Mission Control informed the crew that the final pass was expected to take seven minutes.
Around 20,000 pieces of space junk are tracked down, including old and broken satellites.
Last week, a fragment of an ancient Chinese satellite that was the target of a 2007 missile attack test came uncomfortably close to the space station.
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