High winds and alleged lack of maintenance have caused a 35-metre high Alstom turbine to fall onto the roadside of the N-340 highway in Tarifa, Spain's southernmost and windiest district.
Both Alstom and the local district authority have instigated separate investigations.
The fallen machine is one of two 600kW experimental turbines installed in 1996 by Spanish manufacturer Ecotècnia, which was acquired by Alstom in 2007.
An Alstom spokesman said: "[On] the day of the incident, the machine was out of service. Initial analysis points to a tip break and rotor locking mechanism failure under the extreme meteorological conditions.
"This has most likely led to a collision between the blade and the tower causing the collapse of the structure."
The company says "further root cause analysis is under way."
As a wind hotspot, there are many such early experimental projects among hundreds of small turbines in Tarifa dating back to the early 1990s.
Locals have long complained many machines are neglected as proper maintenance is not profitable.