NASA is investigating the source of an unexplained pong which set off alarms aboard the International Space Station.

NASA spokeswoman Kelly Humphries initially told CNN: "The situation is stable. The crew was asked to put on some protective gear." He said the odour was "not normal".

Later Mike Suffredini, manager of the space station program, said: "It's an irritant, not a life-threatening material."

"All readings well below anything that we would be worried about," he added.

The stench first appeared at 6.23am Houston time. The source is still unknown. ®

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