An unidentified flying object (UFO) was not responsible for damage to a wind turbine in the east England county of Lincolnshire, an interim report by manufacturer Enercon has concluded. Speculation about UFOs ran riot in early January when the turbine, at Ecotricity's Fen Farm wind farm, was found to have lost one blade, with another misshapen after a number of people reported seeing lights in the sky the previous evening. Now Enercon has ruled out collision as a possible cause -- extra-terrestrial or otherwise. Instead it concludes that bolts securing the blade to the hub failed due to material fatigue. So far, Enercon has ruled out bolt defect due to the nature of the failure and is now looking into supporting components on either side of the bolts. If one of these failed, it would induce stress in the bolts beyond their design limits. "We hope to have the results back in a few weeks, says Dale Vince of Ecotricity. "It's a job of separating cause from effect now -- we can see which bits are broken, but which bits failed first is the bit that needs forensic investigation; it's all clever stuff."