Five of the seven astronauts currently aboard the International Space Station (ISS) have been placed on high alert after NASA instructed them to prepare for a possible emergency evacuation due to an air leak detected in part of the station.

According to a NASA statement, the astronauts participating in the Crew-12 mission were instructed to take shelter in the Crew Dragon spacecraft, which remains docked to the ISS, and to put on their spacesuits as a precautionary safety measure.

The directive was issued from NASA’s mission control center as efforts continue to address the leak by the Russian crew operating in that section of the station.

NASA stated that preparations for a possible evacuation are being carried out for safety reasons, while work to locate and repair the leak continues.

NASA and Russia’s space agency Roscosmos, the two main operators of the station, have been in discussions for months regarding the causes and possible solutions for small air leaks detected in the Russian Zvezda service module, one of the main sections of the orbital laboratory, which is about the size of a football field.

The leaks were previously considered limited in scope, but on Monday the air loss increased significantly, according to a senior NASA official cited by Reuters.