A Nasa statement has said that the crew on board the International Space Station (ISS) is safe and that an ammonia leak is possible but not certain.
The official said the crew had evacuated to one section of the ISS after they observed an increase in water loop pressure and then cabin pressure.
This could indicate an ammonia leak, but this is a "worst case scenario", hence the precautionary evacuation.
The statement said that the alert could also have been caused by a "faulty sensor or by a problem in a computer relay box".
Astronauts have been evacuated from the US section of the International Space Station due to an ammonia leak, it has been reported.
The evacuation was reportedly ordered due to a leak of "harmful substances" from the cooling system.
All six members of crew, which includes three Russian astronauts, two American and one Italian, are now holed up in the Russian section of the station.
Russian news agencies report the situation is now under control.
The six astronauts aboard the International Space Station have been celebrating Christmas while orbiting the Earth.
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Conditions will be perfect this Christmas Eve to spot the International Space Station pass over the UK, or was it Santa's sleigh?Read the full story ›
A veteran Russian cosmonaut and two International Space Station crewmates have returned safely to Earth after over five months in orbit.
A Soyuz capsule carrying Maxim Suraev of the Russian space agency, who was commander of the station during the mission, climbed into the Soyuz craft with NASA astronaut Reid Wiseman and German flight engineer Alexander Gerst from the European Space Agency, and landed safely in an icy Kazakhstan.
Astronauts filmed the incredible video by putting a Go Pro camera inside a floating ball of water on the ISS.Read the full story ›
Astronaut Alexander Gerst has shared incredible pictures of Hurricane Gonzalo as the huge storm bears down on Bermuda.
The powerful Category 3 storm could raise coastal seas as much as 10 feet (3 metres).
Gonzalo has already begun to pound Bermuda with wind and heavy surf, bearing down on the tiny British territory.
The storm was centered about 100 miles (165 kilometres) south-southwest of Bermuda this afternoon with top sustained winds of 125 mph (205 kph), according to the US National Hurricane Centre in Miami.
Gonzalo's eye is expected to pass close enough to be considered a direct hit.
The first Russian female to work on board the International Space Station has safely docked with the rest of her crew.
Elena Serova, a 38-year-old trained as space industry engineer, was only the fourth Russian woman in history to fly into space. She will also be the first Russian woman to work aboard the ISS, whose first component was launched in 1998.
After seven years of hard training as a cosmonaut, Serova said in an interview that she had long dreamed about proving that Russian women are able to return to space flights.
Her predecessor, Elena Kondakova, made her second - and last - flight to the Russian space station Mir in 1997 as part of a NASA space shuttle crew.
A US-Russian space crew has blasted off successfully for the International Space Station.
The Russian Soyuz spacecraft lifted off as scheduled from the Russian-leased Baikonur launch facility in Kazakhstan. It was carrying Nasa astronaut Barry Wilmore along with Russians Alexander Samokutyaev and Elena Serova for a six-month stint at the station.
Ms Serova is the first Russian woman to fly to space since 1997, and the fourth woman in the history of the Soviet and Russian space programmes. Valentina Tereshkova became the first woman in space in 1963.