Six astronauts from the ISS are safe and have taken refuge in the Russian part of the space station, after the alarm ended today, according to NASA.

The American space agency, however, was not able to confirm whether the alarm sounded due to an ammonia leak, which had been the earlier announcement by Russian authorities.

Roskosmos, Russia’s space agency, had announced that due to a toxic leak from the cooling system, astronauts were forced to evacuate the American part of the ISS. According to a representative of Roskosmos, there might be need for a “Space walk” to repair the problem.

This problem may also delay the return of SpaceX’s Dragon capsule, to Earth. The capsule transferred supplies to the ISS this week.

The ISS is one of the very few sectors of Russian-American cooperation that were not hurt due to the crisis in the Ukraine.