Nasa has just released a new update, saying that repairs to the air leak on the Russian part of the International Space Station have been paused.

It says the crew members sheltering on the Dragon spacecraft have been told to return to the ISS.

Here's the statement from Nasa spokeswoman Bethany Stevens:

"Roscosmos has paused Friday’s structural repair efforts inside the Zvezda service module transfer tunnel, known as PrK, as more measurements and data is assessed.

"Given this development, NASA has instructed the crew members inside the Dragon spacecraft to end the safe haven procedures and return to planned operations aboard the International Space Station.

"We look forward to working with Roscosmos on a collaborative approach to address the leaks."

Pallab Ghosh
Science correspondent

If the air leak in the Zvezda service module continues to worsen, the ISS crew has a clear emergency exit plan — but it involves splitting up across two separate spacecraft.

Five of the seven crew members are currently sheltering inside the docked SpaceX Crew Dragon "Freedom" spacecraft as a precautionary measure.

Nasa has directed Crew-12 astronauts Jessica Meir, Jack Hathaway, Sophie Adenot and Andrey Fedyaev to take refuge there, along with Nasa astronaut Chris Williams.

They have been told to put on their spacesuits so they are ready to undock and return to Earth at short notice. The Dragon effectively functions as a lifeboat — attached to the station but ready to detach the moment the order is given.

The two Russian cosmonauts, station commander Sergey Kud-Sverchkov and flight engineer Sergei Mikaev, are in a different position entirely.

They remain in the Russian segment - closest to the leak - carrying out the repair work. Their escape route is the separately docked Soyuz MS-28 spacecraft.

However, in a full evacuation, the crew would not simply leave on whichever vehicle they are currently sheltering in.

Crew members are assigned to specific return vehicles before they ever launch.

That means Dragon would carry the four Crew-12 members - Meir, Hathaway, Adenot and Fedyaev - splashing down off the US coast, while Kud-Sverchkov, Mikaev and Williams, all of whom launched together aboard Soyuz MS-28 last November, would make a separate landing on the Kazakh steppe.

For now, Nasa is emphasising this is a precautionary measure, not a full evacuation order. The agency says it is monitoring the situation closely and working with Roscosmos on a more permanent fix. But with suits on and engines ready, the crew is prepared to leave at a moment's notice.

Image source, Reuters

The International Space Station (ISS) has been orbiting the Earth for 25 years and is perhaps the most complex international engineering project ever built.

The space station is made up of Russian and US segments, and there are modules from the European and Japanese space agencies too.

About the length of an American football field, it travels at at 17,000 to 17,500 mph and orbits the Earth roughly every 90 minutes.

As well as conducting experiments that have been sent up to the space station, the astronauts themselves are test subjects and undergo measurements before, during and after their space flights to help us better understand how humans can survive long duration missions - with most crews serving on board for around six months.

Image source, NASA

The picture above, and our live stream at the top of the page, show the latest view of the International Space Station.

As we've reported, the astronauts are sheltering on the Dragon spacecraft, which is docked on the ISS.

Pallab Ghosh
Science correspondent

Nasa has directed five of the seven astronauts currently aboard the ISS to shelter inside the docked SpaceX Crew Dragon "Freedom" spacecraft — designated as a "safe haven" — while two Russian cosmonauts attempt an urgent repair.

The trigger is a worsening air leak in the Russian segment of the station, specifically in the Zvezda service module's transfer tunnel, known as the PrK.

This is not the first time the station has had to deal with this problem — the cracks responsible have persisted on and off for around six years.

However, following the arrival of a Russian cargo ship last month, the Russian Space Agency Roscosmos noticed a fresh slow pressure drop in the tunnel, prompting the decision to move beyond patchwork fixes and attempt a more extensive repair operation today.

Here's the full statement from Nasa spokeswoman Bethany Stevens, released a short while ago:

"The Zvezda service module transfer tunnel, known as PrK, has suffered from cracks and leaks for some time, and has been mitigated by Roscosmos as much as possible to date.

"The cracks have always been a concern that NASA watches very closely. NASA and Roscosmos have been working to determine the root cause of the cracks, and Roscosmos manages the issue through operational mitigation measures and periodic partial-repair efforts.

"Following new leaks, Roscosmos has elected to proceed with a more extensive repair operation on Friday, June 5.

"Out of an abundance of caution, NASA has directed all four of the agency's SpaceX Crew-12 members and NASA astronaut Chris Williams to assume an elevated safety posture in the Dragon spacecraft while the repair is underway.

"We continue to work with our Russian counterparts, along with the rest of the international community that supports the space station, to arrive at a more permanent resolution."

Astronauts aboard the International Space Station have been told to shelter on their spacecraft as repair work is carried out to fix new air leaks, Nasa says.

"Out of an abundance of caution, Nasa has directed all four of the agency's SpaceX Crew-12 members and Nasa astronaut Chris Williams to assume an elevated safety posture in the Dragon spacecraft while the repair is under way," the space agency says.

This is a breaking news story and we'll bring you more information as we have it.