ALISON CHIESA and GRAEME SMITH

A major operation to airlift more than 500 workers from a North Sea oil rig was wound down yesterday afternoon after a suspected bomb threat turned out to be mistaken.

It is understood the incident was sparked after a woman was heard making comments thought to pose a security risk on the Safe Scandinavia rig.

The operation, which would have been the biggest evacuation in the history of North Sea operations but was quickly stood down, was criticised as an "over-reaction" by industry figures after it emerged that the 23-year-old woman, a worker on the rig who has not been named, did not pose a security risk.

She was reported last night to be under the care of doctors on the mainland.

However, Nicol Stephen, the Scottish Liberal Democrat leader who represents Aberdeen South, praised the "professionalism and efficiency" of the evacuation, which he said was the biggest of its kind in 30 years.

Fears that a device was on board the rig's accommodation block prompted a massive operation involving police, coastguard and RAF teams. Aberdeen Coastguard said 161 of the rig's 539 workers were airlifted from the installation, which is attached by bridge to an oil rig in the Britannia field, around 130 miles north-east of Aberdeen.

The emergency-response operation led to eight helicopters being scrambled and 14 put on alert. Justice Secretary Kenny MacAskill was kept informed as events developed over the course of the day.

A police spokeswoman said it was the operating company which took precautionary action to evacuate.

She added: "It has since reversed that decision and it is understood it is returning personnel to the installation."

The woman was expected to undergo police questioning on her arrival. The accommodation block, or "flotel", had been evacuated and the workers moved across the bridge on to the rig after the alarm was raised.

Oil company Britannia Operator said a company response team had been assisting in the co-ordination of support services.

Kathy McGill, managing director of the firm, said in a statement: "We are very relieved that this has turned out to be a false alarm but we obviously had to treat this seriously."

Safety statistics:

  • Last November 159 workers on the Thistle Alpha rig, which lies 120 miles north-east of Sumburgh in Shetland, were airlifted to safety after a fire. There were no casualties
  • The crew of the Ocean Guardian, a semi-submersible rig which was operating 120 miles north-east of Aberdeen, were evacuated last August after a fire broke out.
  • In April last year eight men died after an oil rig support vessel, the Bourbon Dolphin, capsized. Many of the 99 workers on an oil rig thought to be attached to the vessel, 75 miles north-west of Shetland, were evacuated.
  • A gas leak on the Brae Alpha platform in November 2004 led to the evacuation of 139 workers.
  • On 6 July, 1988, 167 workers on the Piper Alpha platform died in a massive explosion.