Astronauts might have to step outside the International Space Station at the weekend to repair a leaking cooling system on the Earth-orbiting spacecraft, Russia’s Interfax news agency reported today.

The US space agency said in a statement that the leak was no danger to the six-member crew, who noticed floating white ammonia, which runs in loops to cool the spacecraft’s power system.

NASA said it was developing plans to re-route power lines to maintain full operation should the loop shut down.

Station commander Chris Hadfield of Canada tweeted that the “serious” situation had been stabilized.

In November, two astronauts stepped out of the spacecraft to fix a similar ammonia leak.