WASHINGTON — Four astronauts will return from the International Space Station more than a month ahead of schedule after an unnamed crew member experienced a medical issue.

NASA has not provided details about the nature of the problem, citing privacy concerns.

The space agency said Thursday the US-Japanese-Russian crew of four will return to Earth in the coming days, earlier than planned.

NASA canceled its first spacewalk of the year because of the health issue.

NASA officials stressed that it was not an onboard emergency, but are "erring on the side of caution for the crew member,” said Dr James Polk, NASA's chief health and medical officer.

“We have a very robust suite of medical hardware on board the International Space Station,” Polk noted during a Thursday news conference. “But we don’t have the complete amount of hardware that I would have in the emergency department, for example, to complete a workup of a patient.

“And in this particular incident,” he added, “we would like to complete that work up, and the best way to complete that workup is on the ground.”

Polk said this was NASA’s first medical evacuation from the space station, although astronauts have been treated aboard for things like toothaches and ear pain.

The crew of four returning home arrived at the orbiting lab via SpaceX in August for a stay of at least six months. The crew included NASA’s Zena Cardman and Mike Fincke, along with Japan’s Kimiya Yui and Russia’s Oleg Platonov.

Fincke and Cardman were supposed to carry out the spacewalk to make preparations for a future rollout of solar panels to provide additional power for the space station.

It was Fincke’s fourth visit to the space station and Yui's second, according to NASA. This was the first spaceflight for Cardman and Platonov.

“I’m proud of the swift effort across the agency thus far to ensure the safety of our astronauts,” NASA administrator Jared Isaacman said.

Three other astronauts are currently living and working aboard the space station, including NASA’s Chris Williams and Russia’s Sergei Mikaev and Sergei Kud-Sverchkov, who launched in November aboard a Soyuz rocket for an eight-month stay. They’re due to return home in the summer.

NASA has tapped SpaceX to eventually bring the space station out of orbit by late 2030 or early 2031. Plans called for a safe re-entry over ocean. — Agencies