A search for a suspected Second World War German submarine in a Labrador river has turned up only a sandy mound of frustration and an unresolved military mystery.

A remote-operated vehicle was used for two days to probe the deep, murky depths of the Churchill River, where a sonar image has suggested that a U-boat may have sunk.

The search over the past week, however, not only didn't add new information to what a prior search had uncovered, it found that the object — first identified two years ago, but not made public until last month — has subsequently been buried by sand and clay that had eroded from nearby cliffs.

Still, diver Brian Corbin says the lack of new evidence hasn't shaken his belief that the object may have been a U-boat.

"We believe what we have is a German submarine," Corbin told CBC News. "We're still getting raised elevation there — there's something there."

The remote-operated vehicle and side-scan sonar technology used in the search launched last week were provided by the Stephan Hopkins Memorial Foundation, a western Newfoundland group that helps recover the bodies of drowning victims.

The theory that a buried mound in the Churchill River appears to match the shape of a U-boat attracted international headlines, as well as some skepticism from military experts.

But Corbin says the new scans did not produce anything to disprove the theory.

"We believe [with the first scan] there was possibly three feet of metal that was detected, so it could be understandable in two years the sedimentation has covered the submarine," Corbin said.

Corbin said his next move is to use a piece of gear called a magnometer, which may provide better detail about the size of the metal object.

"This machine can detect through the sand, and we can use it from above in the boat, 80 or 90 feet [24 or 27 metres], and we believe we can actually pinpoint the end of what we found — the bow and stern," he said.

U-boats had several skirmishes around Newfoundland during the Second World War, including the sinking of the SS Caribou in the Cabot Strait in 1942, and the sinking of four iron ore carriers near Bell Island in Conception Bay in the same year.

There had been no reports of a U-boat as far north as the Churchill River, which is well inland from the Atlantic Ocean. The suspected site, though, is not far from where a military base was built at Happy Valley-Goose Bay during the war. That base survives today as 5 Wing Goose Bay of the Canadian Armed Forces.

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