Photo: Niall Carson/PA
A 328-foot tall wind turbine worth more than £2 million has buckled and collapsed on a mountainside in Northern Ireland.
Unconfirmed reports suggested the blades of the turbine had spun out of control - despite only light wind speeds - before the structure came crashing to the ground on Friday.
Locals claimed the sound of the turbine hitting the mountain could be heard up to seven miles away from the Screggagh wind farm, near Fintona in County Tyrone.
Some people compared it to an explosion while others claimed to have heard the sound of metal grinding throughout the day.
No-one was injured in the incident, which left debris scattered across the wind farm site.
The turbine was one of eight at the site, which opened in 2011 at a total cost of £26 million, implying a project cost of more than £3 million per turbine.
The actual turbine equipment itself cost just over £2m, Screggagh wind farm's owners said. Each has a nominal power-generating capacity of 2.5 megawatts.
Each turbine's tower is almost 200 feet tall, with the rotor blades spanning a diameter of more than 260 feet, giving a total height from base to tip of 328 feet, Screggagh wind farm's owners said.
The remaining seven turbines have been shut down while manufacturers investigate what went wrong. Wind speeds were "medium" or 10 to 12 metres per second, they added.
Doreen Walker, director of Screggagh Windfarm Ltd, said: "There were fortunately no injuries and no personnel on site at the time."
She said: "We are currently investigating the circumstances that led to the collapse of the turbine at Screggagh wind farm.
"We are however satisfied that the site's precautionary health and safety alert processes worked well with local emergency services in attendance within minutes of the incident taking place."
She said officials were "working closely" with Nordex UK, the supplier of the wind farm turbines, to ensure the site is safe.
Buckled metal was left strewn on the mountainside (pic: Niall Carson/PA).
"A further statement will be made once the investigation has been completed and the reasons for the failure confirmed," she added.
German manufacturer Nordex is currently delivering a new, even bigger turbine design for other sites in the UK.
The collapsed wind turbine (pic: Niall Carson/PA).
The accident is not the first safety incident involving Nordex turbines.
In 2012 the company was fined £26,000 after admitting health and safety failings at a site in Stirlingshire where a 19-year-old worker fell 100ft down a turbine to his death.
The company had previously been told to upgrade to a lift system instead of ladders, but the court found there was no link between the safety breaches and the teenager's death.
Defence lawyers in the case said that Nordex UK had been "practically insolvent" in the preceding years.
And in September 2013 an eight-year-old Nordex turbine in a German wind farm reportedly caught fire.
A spokesman for Nordex was unavailable for comment on the Northern Ireland case.
Previous incidents of wind turbines collapsing in the UK include one that fell during a gale in Devon in 2013, which was later blamed on sabotage after it emerged bolts were missing from its base.
Chris Streatfeild, director of health and safety for wind industry body RenewableUK, said: “A thorough investigation is already underway into what happened in this extremely rare incident. The wind industry takes health and safety issues very seriously, and the lessons learned from this will be implemented as swiftly as possible.
“No member of the public has ever been injured by wind turbine operating in the UK. As the trade body representing the wind industry."