The National Aeronautics and Space Administration said the leak, while significant, never jeopardized crew safety.

WSJ: Spacewalkers Replace Space Station Pump

The leak was detected after space station crew reported seeing small white flakes floating away from the station, the space agency said.

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As a result, the "signature" of the pressure drop was very garbled, and sources told MSNBC.com that some space engineers argued there was no increased leak at all, but merely pressure changes caused by these other factors.

MSN: Crew finds ��culprit�� in space station leak

The space station is operating normally aside from the leak, NASA said.

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First detected early Thursday morning, the leak was causing ammonia to enter space at a rate of 5 pounds per day, Mike Suffredini, NASA's space station program manager, told reporters Friday.

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In order to determine the location of the leak, the crew had been sealing off small peripheral modules of the space station while Mission Control looked for accelerated pressure drops inside the sealed-off sections.

MSN: Crew finds ��culprit�� in space station leak

NASA's space station program manager Mike Suffredini said it's a mystery as to why the leak erupted.

WSJ: Spacewalkers Replace Space Station Pump