MOSCOW, September 18 (RIA Novosti) - A problem with an oxygen regeneration system caused an alarming situation Monday on the world's sole civilian orbital station as an alarm went off, Russia's space agency said.

It was initially feared that smoke had emerged on the International Space Station after a short circuit, but the press secretary for the Federal Space Agency played down the concerns.

"An unpleasant smell on board the ISS appeared after an oxygen regeneration system, Elektron, was activated," Igor Panarin said.

Panarin said the system had been switched off and the situation was under control.

He said the crew had turned off the system Sunday after the U.S. Space Shuttle Atlantis undocked from the station. When Russian cosmonaut Pavel Vinogradov and American Jeffrey Williams reactivated the system today, they smelled an unpleasant odor and switched it off again.

This is not the first time the oxygen regenerating systems have failed on the ISS.

Williams and Vinogradov had to replace a hydrogen disposal valve during their first spacewalk. This was necessary to ensure an uninterrupted generation of oxygen for crew members and the disposal of hydrogen used in the process.