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EDINBURGH, Scotland (AP) — What lurks beneath the dark waters of Scotland's Loch Ness?

Newly released documents on display Tuesday in Scotland show that during the 1930s, police in Scotland were convinced some sort of creature inhabited the Highlands lake — so sure, in fact, that they worried about how to protect it from big-game hunters.

The files from the National Archive of Scotland show that local officials asked Britain's Parliament to investigate the issue and confirm the monster's existence — in the interests of science.

"That there is some strange creature in Loch Ness now seems beyond doubt," wrote William Fraser, a senior police officer, "but that the police have any power to protect it is very doubtful."

The Nessie Files, kept secret for 70 years, were revealed as part of an exhibition on government secrecy. The exhibit examines how governments once kept almost everything secret, and how attitudes evolved to move toward more open government in modern times.

Nessie, of course, was the epitome of mystery. The loch in which the monster is said to swim is the deepest inland expanse of water in Britain. At about 750 feet (230 meters) to the bottom, it's even deeper than the North Sea.

The legend of what lies beneath the surface dates to 565 A.D., when an early Christian, St. Columba, is recorded as having driven away a water monster by the power of prayer, the National Archive said.

The documents also offer a glimpse of the collision of centuries-old lake lore with an emerging mass media — a modern effort to document a long-held superstition. The search grew feverish in the 1930s after a surgeon snapped a (now discredited) photo of a black dinosaur-like head rising from the depths.

Archivist Tristram Clarke said the letters reveal that some people sincerely believed there was a monster in the loch — though the cool response from the government suggests there plenty of detractors. If nothing else, Clarke said the Fraser letter proves that the police were under pressure to protect the monster — whatever it was.

Fraser's letter to officials in London warned that he feared hunters Peter Kent and Marion Stirling were "determined to catch the monster dead or alive" and planned to use a "special harpoon gun."

Kent was preparing a major operation including 20 experienced hunters and Fraser said he warned of the "desirability of having the creature left alone."

The idea didn't get very far in the end. The files show that it was deemed better not to kill the monster — or the myth — by stationing cameras or observers around the lake.

Though the sightings proved to be a hoaxes, they didn't stop a Nessie-spotting tourism industry from springing up, together with three-humped cuddle toys, T-shirts and mugs.

"I think Nessie is such an iconic part of Scotland," Clarke said. "The legend lives on. It's almost part of Scotland's identity."

Though the number of sightings has tailed off recently, devoted believers continue to scour the loch. Gary Campbell of the Official Loch Ness monster club lives in hope of finding Nessie one day.

"Fourteen years ago I saw a hump break the water on the loch, I took a double take and then more of it appeared," he said. "I haven't seen anything since, but I keep looking. It probably cost me my social life."

The faithful have long speculated about what the monster is. Some suggest a completely unknown species, or a sturgeon, or even a last surviving dinosaur.

"The reason why the Nessie myth persists is it such a good story," said Lee Barron, a lecturer in media and culture at Northumbria University. "We get a sense of wonder out of the 'what ifs' of it all.

"There are lots of monster in the lake myths around the globe, including the U.S. and Europe, but because of the sightings, the fake photos and the romance of Loch Ness, Nessie is the greatest of them all."