© The TelegraphThe Berwyn Mountains, north Wales
Locals reported hearing a loud bang and saw brilliant light in the sky over the Berwyn Mountains, north Wales, on the evening of January 23, 1974.
Some researchers claimed at the time that the explosion was caused by an alien spaceship crash and then covered up by the authorities.
A search and rescue team from RAF Valley, on the island of Anglesey, was scrambled to look for wreckage but found nothing, the National Archives files show.
A Ministry of Defence investigation concluded the scare was the result of a noisy earth tremor that coincided with a meteor burning up in the atmosphere.
