Reuters published this article:

A hole less than one millimetre in diameter is to blame for a coolant leak from a Russian Soyuz spacecraft docked at the International Space Station (ISS), the head of Russia's Roscosmos space agency said on Monday.

A routine spacewalk by two Russian cosmonauts was cancelled last week after NASA noticed a stream of fluid spewing from the vessel. Temperatures on board the capsule have since risen and Roscosmos has scrambled to investigate the cause and decide how to resolve the issue.

"A preliminary check has shown that there is a small hole, around 0.8 millimetres, which caused the depressurisation," Yuri Borisov, the head of Roscosmos, told Russian state TV on Monday.

The crew were not in danger, Borisov said, and were currently based inside the ISS.

Roscosmos had planned to inspect the capsule with a 17-metre long robotic arm, named the Canadarm2, which performs maintenance, moves supplies and grapples vehicles to the ISS.

Temperatures aboard the Soyuz MS-22 capsule had now stabilised below 30 degrees Celsius (86 degrees Fahrenheit) and the capsule was in working condition, Borisov said. However, he called the situation "clearly not very good" and said that a commission would decide before the end of the month what steps should be taken next.

Roscosmos has advanced plans to potentially deploy a reserve spacecraft to ferry the cosmonauts back to Earth should the docked Soyuz MS-22 prove out of action. Borisov said the reserve spacecraft would be ready to launch by Feb. 19.

Russia has announced plans to walk away from the ISS - one of the few areas of large-scale cooperation between the United States and Russia - and launch its own space station. Borisov, who took over as the head of Roscosmos in July, has said the ISS has outlived its purpose and is "dangerous".