After a crew member aboard the International Space Station suffered an undisclosed medical issue, NASA crews are working to bring the four Crew-11 astronauts back home to Earth earlier than planned.

NASA did not identify the crew member or provide details on the medical concern, citing privacy issues. Crew-11's early return will represent the first medical evacuation in the 25-year history of the ISS, said Dr. James Polk, chief health and medical officer at NASA Headquarters.

“Obviously, this was a serious medical condition. That is why we're pursuing this path," NASA Administrator Jared Isaacman said during a Thursday, Jan. 8, news conference.

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"Crew member is stable. As we mentioned, we're not electing an emergency deorbit. But obviously, as we've already communicated, the capability to diagnose and treat this properly does not live on the International Space Station," Isaacman said.