NASA officials said they plan to bring the crew aboard the International Space Station home early due to what the space agency called a "medical concern" with an unidentified crew member.

They said the astronaut's condition is stable and it is not an emergency evacuation, but they want to err on the side of caution and bring them home for additional testing. Crew 11 is expected to depart on the Crew Dragon Endeavour and return to Earth in the next few days. NASA officials said this is the first controlled medical evacuation in the space station's 25-year history.

The agency stressed Thursday that in the event of an emergency de-orbit, it would have the ability to bring astronauts home within a matter of hours.

The announcement Thursday evening came after NASA scrapped a planned spacewalk earlier in the day.

NASA Chief Health and Medical Officer Dr. James D. Polk said the ISS is equipped with a "robust suite of medical hardware," but it is lacking all the tools that would be needed for a more "complete workup" of a patient. He said the medical issue rose to the level where NASA would prefer to "complete that workup on the ground."

NASA previously said it was looking into "all options, including the possibility of an earlier end to Crew 11's mission." NASA did not specify a timetable for when a new crew would ascend to the ISS but said it was looking into possible earlier dates to launch Crew 12 to the space station.

NASA said it would not be identifying the astronaut in question or giving further details on the medical issue, but earlier said "the matter involved a single crew member who is stable."

Currently aboard the ISS are commander Mike Fincke, flight engineer Zena Cardman, Japanese astronaut Kimiya Yui and Russian cosmonaut Oleg Platonov.

The crew was scheduled to remain aboard the ISS until mid-February.

This is a developing story and will be updated.

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