Astronauts on board the International Space Station were ordered ⁠by NASA to shelter in their spacecraft and prepare for potential evacuation as a Russian crew attempts to fix a worsening leak of air on its portion of the orbital laboratory, NASA said.

The four astronauts of NASA’s Crew-12 mission on ‌the station – two ⁠US astronauts, a French astronaut and Russian cosmonaut – got orders from NASA mission control to enter their Crew Dragon spacecraft docked to the station and ‌don their spacesuits in case the air leak warrants an emergency evacuation, ⁠a NASA official said.

NASA and Russia’s ‌space agency Roscosmos, the station’s two primary operators, have ⁠debated ‌for months over the cause and potential fixes of small air leaks on board Russia’s Zvezda service module, a key structure ⁠of the football field-sized laboratory.

The air leaks have been relatively ⁠minor in recent months but escalated on Monday from a pound of air per day to two pounds, according to a senior NASA official who asked not to be named.