They were tasked with searching for the leak’s source, which worryingly appeared to be rapidly growing.
The ISS members systematically shut compartment hatches and employed an ultrasonic leak detector to collect data.
Using this technique, the trio eventually traced the leak to the Zvezda Service Module.
However, exactly where the leak is inside the Russian module has yet to be found.
Instead, it only appeared larger due to a temporary change in temperature.
NASA said in a statement: “One by one, the crew closed hatches between Zvezda’s aft and forward sections and Zvezda’s passageways to the Pirs Docking Compartment and the Poisk module while using an ultrasonic leak detector to collect data.
“Throughout the night, pressure measurements were taken to try to isolate the source of the leak.
“At the completion of the overnight checks, the crew opened hatches once again between the US and Russian segments and resumed regular activities.”
The space agency added the crew had confirmed the leak was in the main work area of the Zvezda module by Tuesday morning.
NASA said in a blog post: “Additional work is needed to locate the exact source of the leak.”
In August the crew members were ordered to house themselves in the Zvezda compartment while ground control carried out an unsuccessful hunt for the leak.
After this search failed to detect the leak, NASA admitted the source was probably in either the Zvezda or Poisk Mini-Research module, serving as a docking station for incoming spaceships.
NASA said: “With the crew living and working in these modules, it was impossible to achieve the proper environmental conditions necessary for this test.”