Emergency hits International Space Station

The crew of the International Space Station (ISS) evacuated the craft’s U.S. section Wednesday due to fears of a leak of "harmful substances" from the cooling system, but all are safe and the situation is under control, Russian and American space officials said.

The six crew — three Russians, two Americans and an Italian — were now in the Russian section of the orbiting station after what Russian news agency Interfax had initially described as an ammonia leak. Subsequent reports from NASA suggest that a build-up of pressure in the ISS's systems was to blame for the scare, but that this build-up had not resulted in a leak. 

NASA tweeted that the "crew members are safe inside the Russian segment of the ISS following an alarm in the U.S. segment at about 4 a.m. EST."

The agency said that the astronauts and cosmonauts had "responded to coolant loop pressure increases," and that "flight controllers are not sure if the alarm was triggered by a pressure spike, a faulty sensor, or a problem in a computer relay box."

Orbiting from dayside to nightside around the Earth, the space station experiences extreme swings of heat and cold. The station's uses coolant to keep its systems — and occupants — at the right temperature. 

"The U.S. section of the ISS has been isolated, the crew are safe and in the Russian section," said Maxim Matyushin, head of Russia's Mission Control Center. 

Amid fears of a potential coolant leak, the crew went to the Russian section where atmospheric impurities were "within permissible levels."

The statement said it was now up to the United States to decide what further action might have to be taken to deal with the problem in the U.S. section. The crew's health was not in danger, it said. NASA flight and ground crew are now assessing the situation. 

The space laboratory is a 15-nation project which is overseen by Russia and the U.S.

With construction on the station beginning in the 1990s, the orbiting lab represents an example of of post-Cold War cooperation, but Russian-U.S. relations have been strained for the last year by the Ukraine crisis. The Kremlin has said it will reject a U.S. request to prolong the use of the ISS beyond 2020.

Al Jazeera and Reuters