Europe's largest windfarm was shut down after a blade snapped off one of the huge turbines, operators said today.
All 140 turbines at the Whitelee windfarm on Eaglesham Moor near Glasgow are being inspected by engineers following Friday's incident.
ScottishPower Renewables said mechanical failure or a lightning strike could be to blame for the breakage, which it described as 'highly unusual'.
The 150ft, 14-tonne, fibreglass blade broke off in the early hours in windy conditions and landed at the base of its tower.
Operators at the site's 24-hour control room were alerted to the damage by the turbine's automatic system and immediately closed it down.
Sixty-five turbines have begun operating again following an inspection led by turbine manufacturers Siemens.
The examination is expected to be completed by the end of the week.
ScottishPower Renewables managing director Keith Anderson said: 'This type of incident is exceptionally rare and highly unusual.
'However, the safety of our people and the public is our first priority.
'While the investigation into the cause of the incident is ongoing, our engineers continue to conduct an internal and external examination of all turbine blades at the wind farm.'
The Whitelee windfarm, located around 20 minutes from Glasgow city centre, was officially switched on by Scotland's First Minister Alex Salmond in May last year.
Its turbines can generate 322MW of electricity, enough to power 180,000 homes.
Two planned extensions will take the number of turbines to 215 by 2012.