NASA crewmembers aboard the International Space Station (ISS) could return to Earth as soon as Thursday, the U.S. space agency said, after a medical emergency prompted the crew to return from their mission early.

"NASA and SpaceX target undocking Crew-11 from the International Space Station no earlier than 5 p.m. ET on January 14, with splashdown off California targeted for early January 15 depending on weather and recovery conditions," the agency said in a post on X.

Details of the medical evacuation, the first in ISS history, were not provided by officials, though they said it did not result from any kind of injury aboard and that the unidentified crewmember is stable and not in need of an emergency evacuation.

The four astronauts on NASA-SpaceX Crew 11 have been on their mission since August 1. These expeditions generally last around six months, and the crew was already due to return to Earth in the coming weeks.

American astronauts Mike Fincke and Zena Cardman, as well as Japan's Kimiya Yui and Russia's Oleg Platonov, would be returning. Meanwhile, American Chris Williams will stay aboard the international spacecraft to maintain a U.S. presence.

Officials indicated it was possible the next U.S. mission could depart for the ISS earlier than scheduled, but did not provide specifics.

Continuously inhabited since 2000, the ISS serves as a testbed for research that supports deeper space exploration – including eventual missions to Mars.

The ISS is set to be decommissioned after 2030, with its orbit gradually lowered until it breaks up in the atmosphere over a remote part of the Pacific Ocean called Point Nemo, a spacecraft graveyard.