NASA says an ammonia leak has been detected in the cooling system outside the International Space Station, but no crew members are in danger and the station is operating normally.
Crew members at the orbital outpost spotted white flakes of ammonia floating away from the station.
at about 9:30 a.m. EDT on Thursday. Officials said the leak appears to be getting worse.
Ammonia is used to cool the equipment that provides power to the station's systems. Each array of solar battery cells has its own cooling loop.
On its website, NASA said fixing the problem might require shutting down part of the station's cooling system for about 48 hours.
The space station, a $US100 billion research laboratory, is in orbit 400km above Earth.