On Thursday morning, an investigation showed the leak appeared to be on the Russian side of the space station.
Astronauts scrambled Thursday to patch a tiny hole in a Russian capsule that was allowing air to leak from the International Space Station.
Dmitry Rogozin, head of Russian space agency Roscosmos told state news agency TASS that a "micro-fracture" was found in a side compartment of the Soyuz MS-09 spacecraft now docked with the space station.
Controllers based in the United States and Russian Federation say that the six-strong crew crew are not in any danger.
Officials and flight controllers are monitoring the situation as the station's crew works through the procedures, continued NASA.
NASA is not now willing to comment on what caused the leak. He said a 2 millimetere hole may have been caused by the impact of a micrometeorite.
This is not the first time a small leak has sprung up on the space station, which has been continuously inhabited by rotating crews since 2000.
The leak has been isolated to a hole about two millimeters in diameter in the orbital compartment, or upper section, of the Soyuz MS-09 spacecraft attached to the Rassvet module of the Russian segment.
Both natural micrometeoroids (bits of rock left over from the formation of our solar system) and space debris (small pieces of spacecraft that still orbit Earth) are travelling at incredible speeds through space.
The leaking Soyuz - one of two up there - arrived at the orbiting lab in June with three astronauts.
They also need to determine what caused the leak, but at this stage, there's no information released about what might have happened.
Check back for updates on this developing story.