Jan. 8 (UPI) — NASA has postponed Thursday’s spacewalk from the International Space Station because of an astronaut medical issue, the agency said.

The crew member and the illness have not been identified for privacy reasons, and NASA may cut the mission short, it said.

“The situation is stable. NASA will share additional details, including a new date for the upcoming spacewalk, later,” NASA said on Wednesday.

NASA said in a Thursday update: “The matter involved a single crew member who is stable. Safely conducting our missions is our highest priority, and we are actively evaluating all options, including the possibility of an earlier end to Crew-11’s mission. These are the situations NASA and our partners train for and prepare to execute safely.”

Crew-11 launched on Aug. 1 on a SpaceX Crew Dragon rocket with NASA astronauts Zena Cardman and Mike Fincke, Japan Aerospace Exploration Agency astronaut Kimiya Yui, and Roscosmos cosmonaut Oleg Platonov.

There are three other astronauts on the ISS. They are NASA’s Christopher Williams and cosmonauts Sergey Kud-Sverchkov and Sergei Mikayev, who arrived via Russian Soyuz on Nov. 27.