Two Russian cosmonauts used knives and scissors to cut samples from a hole in the Soyuz spacecraft, which Moscow says may have been caused by a workout.
The Roscosmos space agency says it wants to know if the 2mm puncture is made on Earth or in space.
He has ruled out a manufacturing defect and claims that it may have been deliberate sabotage, but Nasa dismissed such speculation.
The "small but dangerous" hole found in the Soyuz MS-09, hooked up with the International Space Station, is now sealed.
The oxygen flow was stopped and the air pressure stabilized, although the three American astronauts, two Russian cosmonauts and one German had never said they were in danger.
Oleg Kenenko and the space window of Sergey Prokopiev were described as "unprecedented in their complexity."