LONDON, England (CNN) -- Britain's Ministry of Defense has released files on UFO sightings dating back to the 1970s, including witness accounts and the government's response.

The ministry on Wednesday released the files as part of a four-year project to transfer all of the UFO documents to the National Archives to make them available to curious members of the public.

The documents include hundreds of police reports taken from witnesses who describe seeing lights or strange objects in the sky, from southern England and Wales up to Northern Ireland.

The files released Wednesday cover 1978 to 1987. The rest, dating from the 1950s and covering recent history, will be released over the coming years.

Reported sightings typically describe various shapes and colors of lights, moving in formation or hovering in the sky.

Witnesses reported orange, red, white and green lights that were diamond-shaped, square, or cigar-shaped. They reported them to police, who have a standard 16-question form specifically for UFO sightings.

"The vast majority of them are just ordinary people who've seen something unusual and thought that they ought to tell someone about it," said David Clarke, a professor at Sheffield Hallam University and a UFO expert who worked with the National Archives on the project.

In one sighting in January 1985, a man near Cardiff, Wales, was closing his living room curtains when he saw an object in the sky. He said it moved "up and down like a bouncing ball," then disappeared behind a mountain.

Two police officers in Woking, south of London, reported seeing a white light in the sky on Christmas morning 1985. The light, they said, moved into the nearby area of Horsell, where author H.G. Wells had placed the Martian landing in his book, "War of the Worlds."

The person who took the report noted the officers were aware of the connection, writing, "Genuine report. Two competent officers slightly embarrassed (Horsell Common features in H.G. Wells)."

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Two other police officers in Edgware, north London, reported seeing an object in the sky in June 1984. They viewed it with binoculars for an hour and sketched a picture, showing a white sphere with a ring of blue and red lights.

"The object moved erratically from side to side, up and down and to and fro, not venturing far from its original position," the officers wrote.

Other reports came from stunned members of the public, pilots, and members of the military.

The Ministry of Defense said it examined the reports and held onto the records solely to determine whether enemy aircraft had infiltrated British airspace. Once it was determined that no enemy aircraft were in the sky, it did not investigate further. Watch why the ministry is revealing what it knows about UFOs »

"The Ministry of Defense has no other interest or role regarding UFO matters and does not consider questions regarding the existence or otherwise of extraterrestrial life-forms," it said Wednesday.

That leaves many of the incidents simply unexplained, such as an April 1984 report made by a senior air traffic controller at an unidentified airfield.

The controller was bringing in a light aircraft for landing when he noticed a series of lights appearing to come down on another runway. The crew of the incoming plane radioed that they saw the lights, too.

All reported that they saw the lights come down "at speed," touch down, and disappear.

"They were so concerned about this, they filed an official report," Clarke said. "But what was the thing that they saw? There's no evidence from the papers that any further investigations were done and it remains a mystery."

In 1979, two years after Steven Spielberg's alien-visitation movie "Close Encounters of the Third Kind," reports of strange sightings had increased and the House of Lords decided to hold a debate on UFOs.

One of the documents released Wednesday is a detailed briefing prepared by the Ministry of Defense for the debate, and it sheds light on the military's position on the matter.

"There is nothing to indicate that ufology (the study of UFOs) is anything but claptrap and no evidence at all of 'alien space craft,'" read the briefing, prepared by the ministry for Lord Strabolgi, then government chief whip.

At least one report in the files has since been explained, however.

A report from August 1985 details the crop circles that two army officers found in a wheat field in Andover, in southern England. They noted one large circle surrounded by four smaller ones, all perfectly round with the wheat pressed down in a clockwise direction.

No tracks led up to the circles, they said.

The farmer called the army officers because he thought the Army Air Corps had created the circles, but the officers said they were stumped.

"None of us could offer any reasonable explanation," they wrote.

It is now known that the crop circles were some of many created by two hoaxers named Doug Bowers and Dave Chorley, according to Clarke.

"Doug and Dave," as they were called, came forward in 1990 to say they created the circles with a garden roller and planks of wood, Clarke said.

"We now know that this particular circle near Andover was one of the ones that was created as a hoax by these two men," he said.

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