Dale Vince of Ecotricity says there is no explanation
UFO enthusiasts are claiming damage to a Lincolnshire wind farm turbine was caused by a mystery aircraft.
The turbine at Conisholme lost one 66ft (20m) blade and another was badly damaged in the early hours of Sunday.
County councillor for the area Robert Palmer said he had seen a "round, white light that seemed to be hovering".
Ecotricity, which owns the site, said while investigations continued they were not ruling anything out - but the extent of damage was "unique".
The turbine is one of 20 at the Conisholme site, which has been only been fully operational since April 2008. The broken blade has been recovered and is being examined.
Local ufologists said they had received many reports of activity in the area and had teams searching for clues.
To make one of these blades fall off, or to bend it, takes a lot
Dale Vince, Ecotricity
Mr Palmer said: "I actually saw a white light - a round, white light that seemed to be hovering.
"That is the only way I can explain it - it wasn't a flare-like light - it was just round, white light with a slight red edge to it that seemed to be over the wind turbines."
Dale Vince, founder of Ecotricity, said the company was keeping an open mind about the incident.
"We don't have an explanation at the moment as to what the cause was," he said.
"We have been crawling all over it and have sent bits off for analysis to see if we can work out what caused it.
"Until we have some idea, some plausible explanation that it was not a UFO, I don't think we should rule it out".
He added: "To make one of these blades fall off, or to bend it, takes a lot."
Russ Kellett, from the Flying Saucer Bureau, said witnesses had told him of activity in the area.
"One saw what they at first thought was a low-flying aircraft on the Saturday evening and another heard a loud banging in the early hours of Sunday," he said.
"This is the second most reports of activity we have ever had - I have had over 30 phone calls and emails.
"To hit two of the blades, any object must have been about 170ft long."
But some technical experts have suggested a more mundane explanation.
Dr Peter Schubel, from the University of Nottingham, is an expert in the design and manufacture of wind turbine blades.
He said that if the turbine blade was still, it would take the equivalent of a 10-tonne load to do that kind of damage, but if it was rotating, or hit by a moving object, the force could be a lot less.
He said of the possible cause: "It's definitely not a bird. It could be ice thrown from a neighbouring turbine that struck it.
"Most turbines have an anti-icing system on the blades and maybe it failed to prevent the ice build-up."
The Ministry of Defence said it was not looking into the incident.
A spokesman said: "The MoD examines reports solely to establish whether UK airspace may have been compromised by hostile or unauthorised military activity.
"Unless there's evidence of a potential threat, there's no attempt to identify the nature of each sighting reported."
Ecotricity said it hoped to have the turbine back in action within a week.
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