NASA and the Russian space agency have decided to isolate the two-man crew on board the International Space Station for several days, while experts try to locate the source of a worrying air leak that has caused a drop in pressure inside the station.
The two crewmen on the space station might spend up to five days in one module to allow experts in the United States and Russia to pinpoint the source of the slow leak.
The plan is to close off all hatches between the four main modules, and then monitor them independently.
American astronaut Michael Foale and Russian cosmonaut Alexander Kaleri will stay in the Russian-built Zvezda module, where their cargo ship is docked, and where toilet and kitchen facilities are located.
The leak was first discovered in late December, and is not considered life-threatening to the crew.
The number of crew on board has been cut substantially since the Columbia space shuttle disintegrated on reentry into earth's atmosphere last February, killing all seven astronauts on board.
Since then, all cargo and manned flights to and from the space station have been made from Russia's main space facility at the Baikonur Cosmodrome in Kazakhstan.