NASA senior adviser and press secretary Bethany Stevens wrote on X that astronauts aboard the International Space Station have quickly shifted into SpaceX's Dragon spacecraft and are prepared to evacuate if needed, after cracks and leaks in the Zvezda service module transfer tunnel appeared to worsen.

"The Zvezda service module transfer tunnel, known as PrK, has suffered from cracks and leaks for some time, and has been mitigated by Roscosmos as much as possible to date. The cracks have always been a concern that NASA watches very closely," Stevens said.

According to NASA, the Zvezda service module is 43 feet long and contains living quarters, life support systems, communications systems, electrical power distribution systems, data processing systems, flight control systems, and propulsion systems.

Stevens continued, "The cracks have always been a concern that NASA watches very closely. NASA and Roscosmos have been working to determine the root cause of the cracks, and Roscosmos manages the issue through operational mitigation measures and periodic partial-repair efforts."

Out of caution, NASA ordered all four SpaceX Crew-12 members, along with NASA astronaut Chris Williams, to be on high alert inside Dragon during the repair.

NASA said it continues to work with Roscosmos and other station partners toward a more permanent fix for the long-running issue.

Reuters cited a senior NASA official who said the air leak has been monitored over the last few months but significantly worsened earlier this week, increasing from a loss of one pound of air per day to two pounds per day.