The wreck of a World War II German submarine off Norway's coast should be covered with sand to contain its cargo of environmentally damaging mercury, a study said Tuesday.

The submarine U-864 was torpedoed and sunk by the British submarine Venturer off western Norway on Feb. 9, 1945. Its wreckage, found by the Royal Norwegian Navy in March 2003, is believed to have about 70 tons of mercury aboard.

The submarine was sunk while trying to get to Japan, a German ally, with mercury for weapons production.

Studies revealed high levels of mercury around the wreck, which is in 500 feet of water about 2 1/2 miles off the western Norway island of Fedje.

In a report Tuesday, the Norwegian coastal administration recommended encasing the submarine in special sand, with a reinforced upper layer to prevent corrosion.

"Worldwide, about 30 large-scale encasing and coverage operations of mercury contaminated debris have been performed in the past 20 years," said the report. It said the measures were proven and provided permanent environmental protection.

If absorbed by fish, mercury can be passed on to humans in food, possibly harming their health.

The Norwegian Ministry of Fisheries and Coastal Affairs said it would be reviewing the report