LAKE TOPLITZ, Austria (AP) _ In the cold waters of a pristine Alpine lake, an American salvage crew is trying to solve some of the last mysteries of World War II _ what secrets or treasures did the Nazis hide here in the chaotic, final days of the conflict.

Since mid-June, the crew has been using state-of-the-art sonar and video equipment to scan the floor of Lake Toplitz to determine once and for all whether cases of secret documents, gold and precious stones are still lying more than 300 feet beneath its waters.

``We hope once we come off (the project) we will be able to say: This is what's there and this is what's not,'' said Scott Pelley, a correspondent for CBS News, which financed the project with the Simon Wiesenthal Center of Los Angeles.

The one-mile- long lake lies in the Salzkammergut region in the heart of Austria, sheltered on three sides by steep limestone faces and reachable only by a narrow, wooded path, was used by the Nazis as a secret marine warfare testing station starting in 1943.

Two years later, with defeat starring them in the face, the Nazis apparently used the lake to hide evidence of their crimes. Workmen under SS guard were seen dumping heavy metal cases into the waters.

No one is sure exactly what was deposited here. For more than a half century, however, rumors have spread that the cases included gold, precious stamp collections, diamonds and other valuables looted by the Nazis from Jews in occupied Europe during the war.

``They know the Nazis were hiding treasures in the area, '' said Albrecht Syen, whose family runs a green-shuttered restaurant, the only building on the lake. ``So they must be in Lake Toplitz.''

The lake itself has fed the legend of lost treasure. Over the years, divers have salvaged more than 18 cases stuffed with documents and counterfeit currency, as well as enormous rusted mines and parts of rockets.

In 1959, the lake yielded millions of dollars worth of fake British pound notes, as well as secret documents detailing the Nazis official counterfeiting operation aimed at devaluing the British currency by flooding markets with fake notes.

More than 14 years later, the Austrian government salvaged more trunks stuffed with fake British pounds and other documents.

The current operation took shape last year when Pelley and CBS television producer Bill Owens heard of the legend of Lake Toplitz from an Israeli colleague. They became intrigued by this unsolved piece of the World War II puzzle that remains little known in the United States.

``Our purpose here, what led us here, was never the story of gold dumped into the lake,'' Owens said. ``It was more the history of World War II dumped into the lake by the SS.''

To do this, they recruited a professional salvage company, Oceaneering Technologies, to map the floor of the lake using remotely operated video-sonar machines.

According to Ridge Albaugh, Oceaneering's senior project manager for the Toplitz search, the operation was hampered by the number of trees covering the lake floor, making it difficult for the machines to squeeze beneath the branches to scan the bottom.

Even if the team pulls up crates of gold or other valuables, the only thing they would be allowed to keep are documents. Anything else must be turned over to the Austrian government.

No matter what happens, neither the Austrians nor the Americans worry that coming up empty handed will kill the intrigue surrounding the lake.

``People are going to talk about this lake and dream about this lake no matter what we find,'' said Pelley. ``Its too much fun to talk about _ it's like the Loch Ness monster.''

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On the Net: http://www.toplitzsee.at/