Ministry of Defence files on what conspiracy theory fans believe may have been a UFO crash in North Wales are expected to be released next year.

The Berwyn Mountains incident sparked mystery in 1974 with unexplained lights in the sky, an earthquake and secretive men in suits.

MoD chiefs confirmed yesterday they are publishing a raft of so-called UFO (Unidentified Flying Object) files stretching back to the 1960s.

This is because of the huge number of inquiries on UFOs.

The Berwyn Mountains incident happened on January 20, 1974.

The people of Llandderfel and Llandrillo villages in the Berwyn mountains near Bala, sat down to that evening's TV.

But the quiet was shattered by the rumbles of an earthquake, registering 3.5 on the Richter scale.

As people ran from their houses, fearing another tremor, they witnessed a blaze of light on the mountainside above.

A local nurse and her daughters claimed they watched as a huge egg-shaped craft lay on the ground with a pulsating orange and red glow.

Police and the military converged on the hills, expecting to discover a crashed passenger jet - but what they did find has never been divulged.

Some think it was an experimental man-made top secret military aircraft, possibly a prototype Stealth bomber.

Local farmer Hugh Lloyd was just 14 at the time.

He told the Daily Post: " It was pretty scary. I have never experienced anything like it.

"It was pretty dark. You could hardly see anything on the mountain and then all of a sudden this incredibly bright light lit up the sky, like an arc welder, two or three miles away, lasting for about 20-30 seconds. You could make out details in the countryside around."

In the days following, scientists and investigators, some of whom could have been from official departments, combed the area.

Mr Lloyd was questioned about the incident, the light and asked exactly what it looked like. "I do not believe that it was a UFO but I would like to find out exactly what it was."

Although the MoD would not confirm categorically the incident - widely dubbed the "Welsh Roswell" - would be in the documents, it said a large amount of material would be released.

An MoD spokeswoman said: "There is no date set but it will be published next year.

"It is going to take time because there are a lot of handwritten documents."