Astronauts aboard the International Space Station (ISS) were placed on alert and instructed to prepare for a possible evacuation after concerns grew over a worsening air leak in the Russian segment of the orbiting laboratory, according to NASA.The precautionary measures were taken as Russian crew members worked to contain and repair the leak, which has drawn increased attention from mission officials monitoring the station’s safety systems.NASA said the four astronauts from the Crew-12 mission — comprising two American astronauts, one French astronaut and one Russian cosmonaut — were directed by mission control at 9:04 a.m. ET on Monday to move into the docked Crew Dragon spacecraft and put on their spacesuits.NASA said the astronauts were ordered to shelter inside their spacecraft as a precaution while engineers and Russian specialists assessed the extent of the issue and attempted repairs on the affected section of the ISS.