The oil major said the escape was located several hundred metres away from the unit in pipeline infrastructure.

It had planned to take all non-essential staff off Curlew on Wednesday after bubbling was spotted on the sea surface.

A Shell spokeswoman told the Courier newspaper: "Shell UK can confirm that a release of gas occurred from infrastructure in the vicinity of Shell's Curlew floating production, storage and offloading vessel (FPSO) located approximately 130 miles south east of Aberdeen late on Monday, January 19, 2015.

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