Three Scottish windfarms were "switched off" yesterday after a massive turbine collapsed in high winds.

The machine, which stands more than 200ft tall at a windfarm in Argyll, apparently "bent in half" during the storm conditions that swept Scotland on Thursday.

Operator Scottish Power stopped the 26-turbine facility ahead of a probe into the cause of the collapse.

The energy giant also switched off two windfarms in the south of Scotland which use the same Vestas V47 turbines.

Last night, Wolf-gerrit Fruh, a senior lecturer in energy engineering at Heriot-Watt University in Edinburgh, described the incident as "extremely unusual".

It is understood the collapse at the Beinn an Tuirc windfarm in Argyll and Bute on Thursday afternoon, as winds reached gusts of 50mph locally, is the first of its kind north of the border.

Mr Fruh said: "It's the first time I have heard of one falling over."

He added: "They are designed to withstand strong winds."

It is understood that the 72 machines that have been switched off represent about 10% of all the wind turbines in Scotland.

But Mr Fruh said the move was unlikely to effect energy production.

"At the moment it's a drop in the ocean," he said.

"I don't think this particular incident is a sign of other things to come. It's a very isolated incident."

But Bob Graham, chairman of Highlands Against Windfarms, warned that turbine collapses are likely to increase as more windfarms are built in Scotland.

A Scottish Power spokesman confirmed no one was injured in the incident in which the tower bent in half, leaving the blades on the ground.

The £21million windfarm, 10 miles north of Campbeltown, which has an output of 30 megawatts, was switched off shortly afterwards.

He added: "A team of specialist engineers, including representatives of the manufacturers, are going to investigate and try to understand what caused it."

It is understood that among the issues being probed will be whether the blades were moving at the time of the incident - they should automatically stop in strong winds.

Dunlaw windfarm, a 26-turbine base near Lauder in the Borders, and the 20-turbine Hare Hill facility, close to New Cumnock, Ayrshire, were also shut down "as a precautionary measure". They will be reopened once each turbine has been inspected.

Shetland Aerogenerators, which operates three Vestas V47s at Burradale windfarm, near Lerwick, Shetland, was advised by the manufacturers to "monitor the situation".

Alan Owen, lecturer in engineering at Robert Gordon University in Aberdeen, said: "Common wind turbine failure could be due to materials, design, or fabrication, and a repeated series of strong gusts could produce forces which were not originally envisaged by the designer."

Earlier this year one man died after a turbine collapsed in Oregon in the US. The engineer was at the top of the Siemens machine when it fell during 25mph winds.