Russia reports 'non-standard' air leak on Space Station
Russia's space agency, Roscosmos, said in a statement that after analysis and a search for the leak "it was established that the spot is located in the Zvezda (star) service module, which contains scientific equipment."
It said a search was now underfoot to pinpoint the exact location, saying the situation "is not dangerous for the life and health of the ISS crew and does not prevent the ISS continuing manned flight."
"It's not critical in the near future," said Sergei Krikalyov, the executive director of Russia's manned space programmes, in a televised comment.
He said the crew were now resting but hoped to find the precise spot and fix the leak on Wednesday.
"That's not for sure," he added, saying there was quite a large area to search.
"We have time. The leak exists of course. It's not good that it's there, but it's not critical," he said.
NASA said that the leak had appeared to grow in size overnight Monday to Tuesday and the crew were awakened by flight controllers to carry out a search.
Previously, astronauts had searched for the source of the leak in the US segment of the station using an ultrasound detector.
The incident comes after astronauts in 2018 found a hole in the wall of a Russian-made Soyuz space capsule docked onto the ISS.
The cause of the hole has not yet been made public.
Three new crew members, Russians Sergei Ryzhikov and Sergei Kud-Sverchkov and NASA astronaut Kate Rubins, are set to arrive in a Russian Soyuz spacecraft due to launch October 14.