The leak was detected after space station crew reported seeing small white flakes floating away from the station, the space agency said.
The space station crew has been limited to two full-time residents since last year's suspension of space shuttle flights in the wake of the Columbia accident.
BBC: NEWS | Science/Nature | Astronauts may get time extension
Nyberg, 43, spent two weeks in space in 2008 as part of a U.S. space shuttle crew.
Usachev, Voss and Helms, having completed 156 days on Alpha, now become members of the space shuttle crew.
The December Soyuz mission will restore the space station crew size to six and continue normal crew rotations.
Suffredini said Monday that space station crew is well-supplied due to the delivery of goods by the final U.S. shuttle mission carried out by Atlantis last month.
The Progress M-12M that went down last week was to deliver more than 3.8 tons of cargo to the space station crew, including food supplies, medical equipment, personal hygiene items and scientific equipment needed for experiments, according to Roscosmos and space officials.
Shuttle Endeavour, which had been docked with the Mir space station, unhooked on Thursday, about a half hour after the Russian space agency launched a Soyuz rocket with three new crew members for the space station.
After a two-day journey aboard the Soyuz capsule, the crew will dock with the space station, overlapping briefly with the current crew - station commander Mike Fossum of Nasa, Japan's Satoshi Furukawa and Russia's Sergei Volkov - who will then return to earth.
He acknowledged that leaving the space station without any crew members increased the risk for trouble.
Still, the space station's crew -- which also includes three Russian cosmonauts -- were never in danger because of it, NASA said.
Our second goal is to develop and test a new space craft, the crew exploration vehicle, by 2008, and to conduct the first manned mission no later than 2014.
CNN: Bush: 'It is time for America to take the next steps' in space
The agency would start regulating space vehicles to ensure crew and passenger safety only if the operation of those vehicles resulted in death, serious injury or a dangerous close call.
Early in the year, a Soyuz rocket carrying an unmanned Progress spacecraft suffered a launch failure, a failure that had some concerned that NASA might decide to leave the International Space Station without a crew.
Science editor Alan Boyle's blog: NASA and the European Space Agency have signed an agreement calling for the Europeans to provide the service module for the Orion space capsule, the U.S. space agency's crew vehicle for exploration beyond Earth orbit.
MSN: Mars rover survives 'brain transplant' with flying colors
The International Space Station will gain its full crew complement of six next month, when NASA astronaut Don Pettit, European Space Agency astronaut Andre Kuipers, and cosmonaut Oleg Kononenko launch from Kazakhstan on December 21.
And it's possible space officials might decide that the longer, old-fashioned way -- allowing the crew to get its space legs over two days, however cramped they might be -- is preferable, depending on how this mission goes, Humphries said.
In 1992, the U.S. space shuttle Endeavour took off with a crew that included Mark Lee and Jan Davis, the first married couple in space.
The crew of the space station is expected to rise from three to six in mid-2009.
BBC: NEWS | Science/Nature | Endeavour launched from Florida
The crew of the space shuttle Challenger honored us by the manner in which they lived their lives.
The crew of the Space Station will open the hatch of Dragon tomorrow.
FORBES: SpaceX Dragon Successfully Berths With Space Station
After unloading the Dragon, the crew of the Space Station will reload it with new cargo for departure to Earth on October 28.
FORBES: Big Day For SpaceX As Elon Musk Tells His Mom 'I Haven't Started Yet'
And in 2012 the crew of the space station were ordered into escape capsules as a precaution after a piece of debris passed close by.
But then the Russian space program successfully launched a crew of three to the ISS earlier this week, giving the station its first full complement since September.
"We're going to do what's safest for the crew and for the space station, " Suffredini said.
Wubbo Ockels, a former European Space Agency astronaut, and seven crew members were stranded on board Ecolution seven miles off the coast.
If the world ever makes it to Prometheus, it will probably be on a Russian space ship or have a Russian crew.
The Progress spacecraft being delivered by the rocket is unmanned, and filled with supplies for the crew of the International Space Station.
While Padalka and Malenchenko worked outside, 5h3 four other members of the space station's Expedition 32 crew remained inside the orbiting lab.
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