Norway has discovered that a Soviet-era submarine that sank in the Norwegian Sea 30 years ago is leaking radiation at levels up to 800,000 times higher than what is normal.

Using a remote controlled vehicle to probe the wreck, researchers found extensive damage to the Komsomolets sub, which lies more than 5,500 feet down on the seafloor. Their investigation revealed the exceptionally high radiation level in the area around a ventilation duct at the wreck, according to the Norwegian Radiation and Nuclear Safety Authority.

The highest measurement researchers recorded stood at 800 Becquerel per liter; radiation levels in that body of water typically remain around 0.001 Bq per liter, the authority said.

"This is, of course, a higher level than we would usually measure out at sea but the levels we have found now are not alarming," said expedition leader Hilde Elise Heldal of the Norwegian Institute of Marine Research, according to Reuters.

Two nuclear warheads and a nuclear reactor remain on board the defunct 400-foot-long submarine. Norwegian and Russian authorities have periodically examined the wreck to monitor radiation levels and assess the pollution risks. Russian investigators had previously found small radiation leaks there in the 1990s and in 2007, the Norwegian Radiation and Nuclear Safety Authority said.

Heldal said team members "weren't surprised" to discover elevated radiation levels this time around, the BBC reported.

The discovery should not cause alarm, she added. Radioactive cesium is easily diluted in the depths of the Norwegian Sea, and few fish live in the area surrounding the wreck.

"What we have found during has very little impact on Norwegian fish and seafood," Heldal said, according to the Associated Press. "In general, cesium levels in the Norwegian Sea are very low, and as the wreck is so deep, the pollution from Komsomolets is quickly diluted."

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