A second warning over wind farms has been issued after a series of investigations into safety following the collapse of two turbines during gales.
The Canadian manufacturer of the 111ft (34m) turbine which toppled in Devon last month has blamed "grout" and "the manner in which the tower was fixed" for the tower's collapse.
Endurance Wind Power, makers of the E3120 turbine, which was found crumpled on farmland in Bradworthy, has also dismissed speculation that sabotage may have contributed to the fall.
But the company also said it has identified a further 29 turbines that might have been affected by the same problem as the East Ash Farm equipment, some of them thought to be in Somerset, Devon and Cornwall. It says the "early installations affected" would receive remedial works to the foundations, free of charge, with many having already been "returned to service".
In a statement Endurance said it had concluded that "a problem with the structural grout and the manner in which the tower was fixed to the foundation" had "resulted in the tower collapse".
The findings come after Glasgow-based Gaia Wind wrote to more than a dozen owners after its 60ft (18m) tower was toppled at Winsdon Farm, North Petherwin – the family farm of Liberal Democrat Cornwall Councillor Adam Paynter.
Experts said the details raise further safety concerns about the industry, claiming that the proliferation of wind turbines would inevitably lead to a serious accident.