The leak of coolant from the Russian Soyuz spacecraft docked to the International Space Station (ISS) is caused by a hole with a diameter of less than one millimeter, the head of the Russian space agency Roscosmos said on Monday, Reuters reports.

A routine spacewalk of two Russian cosmonauts was canceled last week after NASA spotted a jet of liquid ejecting from the Union capsule. Since then, the temperature on board the Russian capsule has increased, and Roscosmos is trying to investigate the cause of the incident and decide how to solve this technical problem.

“A preliminary inspection showed that there is a small hole, about 0.8 millimeters, which caused the depressurization,” Yuriy Borisov, director of Roscosmos, told Russian state television on Monday, Agerpres reported.

According to a Russian official, the crew is safe and is now inside the ISS.

Roscosmos intended to inspect the capsule using a 17-meter-long robotic arm called Canadarm2, which performs maintenance operations, moves supplies and catches orbiters near the ISS.

The temperature inside the Soyuz MS-22 capsule has stabilized below 30 degrees Celsius, and the capsule is operating within normal parameters, Yuriy Borisov said. However, he said that the situation is “clearly not very good”, noting that the commission will decide by the end of this month what further action will be taken.

At one point, Roscosmos talked about the possible launch of a backup capsule to deliver astronauts to Earth if the Soyuz MS-22 could no longer be used. Yuriy Borisov reported that the spare capsule could be ready for launch by February 19.

Moscow has announced that it plans to abandon the ISS project – one of the few areas of cooperation between the US and Russia since the invasion of Ukraine – and launch its own space station. Yuriy Borisov, who headed Roscosmos in July, said that the ISS had outlived its purpose and had become “dangerous”.