NASA has announced that four astronauts aboard the International Space Station (ISS) will return to Earth over a month early due to medical issues. This unprecedented evacuation marks the first of its kind in the ISS’s 25-year history.

Due to medical privacy regulations, NASA refrained from disclosing specific details, including the identities of the affected astronauts and the nature of their medical conditions. However, officials confirmed that the overall situation remains stable.

Speaking at a recent news conference, NASA Administrator Jared Isaacman stated that the astronauts are expected to return home in the coming days. An exact timeline for undocking and landing has not yet been provided.

“After consulting with Medical Officer of Health Dr. J.D. Polk and leadership across the agency, we believe returning Crew-11 early is in the best interest of the astronauts,” Isaacman said in a statement.

Isaacman noted that further updates would be available within the next 48 hours.

The Crew-11 team evacuating the ISS consists of NASA astronauts Zena Cardman and Mike Finke, Japanese cosmonaut Kamiya Yui, and Russian cosmonaut Oleg Platonov. They had originally arrived in early August with plans to stay until late February.

Dr. Polk reassured the public that the situation is stable, clarifying that the decision to evacuate was made for the well-being of the astronauts, not due to an emergency.

“While the ISS is equipped with sophisticated medical technology, it cannot match the complete resources of a hospital emergency department for thorough patient evaluations,” Polk explained. “In this case, there were multiple medical events which necessitated a careful assessment of the astronauts’ health.”

NASA first made the medical concerns public on Wednesday, when it was revealed that Cardman and Finke were deferring a scheduled spacewalk.

Following the early return of Crew-11, NASA will operate with just one astronaut on the ISS, who will oversee ongoing U.S. scientific operations. Flight engineer Chris Williams launched aboard a Russian Soyuz spacecraft on November 27, accompanied by Russian cosmonauts Oleg Platonov, Sergei Kud-Sverchkov, and Sergei Mikayev.

The subsequent crew is slated to launch to the ISS in mid-February, but Isaacman indicated that NASA may evaluate enhancements for this upcoming mission, known as Crew-12.

This week’s developments present Isaacman’s first significant challenge since taking office on December 18.