(CNN) -- NASA scaled back operations on the International Space Station on Wednesday after discovering a problem with a cooling system.
A pump on one of the station's two external cooling loops shut down after hitting a temperature limit, NASA said.
Teams worked to get the cooling loop back up and running, NASA said. Experts suspect a malfunctioning valve may have caused the problem, but they're still trying to figure out how to fix it.
The station and crew aboard were never in any danger, NASA said.
The external cooling loops are systems that circulate ammonia outside the station to keep equipment cool.
Officials discovered the malfunctioning loop was producing too much ammonia Wednesday morning, NASA spokesman Josh Byerly said.
Teams have shut down some non-critical systems on the station as a result of the problem, NASA said.
The space station's life support system is still up and running.
Officials could determine that an emergency spacewalk is the best way to fix the failed pump -- something they've done in the past.
But it's too soon to tell whether that's the best option.
The current mission of the space station, officially called Expedition 38, is scheduled to fly until March 2014.
The six-person crew consists of NASA astronauts Mike Hopkins and Rick Mastracchio of the United States; Russians Mikhail Tyurin, Sergey Ryazanskiy and Oleg Kotov; and Koichi Wakata of Japan.
CNN's Drew Iden contributed to this report.
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