The Canadian manufacturer of a large wind turbine which toppled during gales has denied the device was faulty, following an internal investigation.
But the collapse in Devon last week has prompted a fresh probe by the firm into the safety of 20 identical models, including some at sites in the Westcountry.
Parallel investigations by the Health and Safety Executive and installers Dulas Ltd are continuing into how the 111ft (34m) turbine crashed to the ground on farmland in Bradworthy, less than three years after it was commissioned.
Unconfirmed rumours circulated around the local community that the equipment at East Ash Farm had been sabotaged by protesters amid claims that bolts were missing from the steel structure.
Concerns over turbines were raised and Energy Secretary Ed Davey issued a warning in the House of Commons to operators to make sure their equipment was safe or face claims for damages.
Endurance Wind Power, the company which made the E3120 turbine, has now begun a "precautionary" investigation into 20 of its 300 UK turbines, which were erected around the same time as the East Ash tower.
Precise details have not been released but the firm has 27 sites listed on its website as being operational in Devon, Cornwall and Somerset, mostly installed in the past two to three years.
In a statement the firm said: "While just four days into our investigation, we can report this incident was not related to a failure or malfunction of the tower or turbine and that neither the tower nor turbine caused or contributed to the collapse.
"We are working co-operatively with the dealer that installed the turbine and the engineering firm that designed and supplied its foundation to understand the precise cause of the problem.
"As a precautionary measure, approximately 20 installations that occurred during the same time period are also being inspected.
"Communication with dealers and customers has been often, fluid, and transparent since the incident occurred."
The East Ash collapse was followed by a smaller turbine fall at the family home of Cornwall Councillor Adam Paynter less than 20 miles away across the border in North Petherwin.
The Health and Safety Executive confirmed it was still investigating the Devon collapse, as it occurred at a workplace, but not the Cornish incident, which took place on "private property".
An HSE spokesperson said: "HSE was made aware a wind turbine incident last week in Bradworthy, Devon.
"An HSE inspector visited the site on Wednesday 30 January, and we are now investigating."