The wreck of a Soviet nuclear submarine which sunk in the Barents Sea after a fire in 1989 is emitting high levels of radiation, a joint Russian and Norwegian investigative team has reported.

The Komsomolets was a nuclear-powered titanium-hulled attack submarine capable of deep-diving and equipped with two torpedoes carrying nuclear warheads.

The wreck lies 1,680m, roughly one mile, beneath the waves off Bear Island, in the western Barents Sea around 260 miles northwest of the Norwegian coast.

On Monday afternoon a remote-controlled mini-sub took water samples from a ventilation pipe on the submarine with one reading indicating radiation levels are up to 100,000 times higher than those in normal sea water.

Low levels of radiation have occasionally been detected at the wreck over the past 30 years by both Russian and Norwegian research teams.

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The last time radiation was measured was in 2008, when a Russian scientists said they had detected a small radioactive leak.

“The results are preliminary. We will examine the samples thoroughly when we get home,” Hilde Elise Heldal of the Norwegian Institute of Marine Research told Norway’s TV2 broadcaster.

She said despite the readings, the radiation levels do not threaten fishing or the scientific teams working in the area.

While operating the remote sub, the scientists witnessed an “occasional cloud” rising from the ventilation pipe. The team believes the pipe may have direct contact with the vessel’s radioactive cargo.

“We have observed a kind of cloud coming out of this hole once in a while. In connection with the test in which we measured pollution, a cloud came out of the hole. This may indicate that the pollution comes out in pulses,” Dr Heldal said.

The team suggested the ventilation hole at the top of the submarine tower was in direct contact with the reactor inside the wreck.

According to TV2, researchers will now monitor the opening of the pipe more closely for the rest of the research period, which is scheduled to finish on Thursday.

Dr Heldal said the cloud could be caused by ocean currents, tides or other conditions related to ocean movements.

The fire on 7 April 1989 began due to a short circuit in the ship’s engine room. The vessel was able to surface for around five hours. A total of 42 of 69 crew members were killed, mostly of hypothermia while awaiting rescue from the freezing waters.

Just four people were killed from the initial fire and smoke.

The new research was undertaken by the Go Sars research vessel, using a new type of remote submersible craft which gives more accurate readings than previous surveys.

“We are getting closer to the wreck than ever before, and get an even better sampling,” Dr Heldal said.

Ahead of the latest mission to test the submarine, Ingar Amundsen, the director of Norway’s Radiation Protection and Nuclear Safety Directorate said: “The new surveys that Norway and Russia are about to launch are important for understanding the pollution risk posed by Komsomolets.”

The news of Komsomolets’ radioactive leak comes days after the Russian government confirmed a fire had broken out on a top secret nuclear-powered submarine killing 14 sailors, in an incident which also occurred in the Barents Sea.

A high-ranking military official reportedly said the sailors who fought the blaze and died had averted a “planetary catastrophe”.

The incident remains shrouded in mystery after the Russian government refused to reveal the submarine’s name and its mission, claiming them as state secrets.

However, the Kremlin has said the accident was sparked by a fire in the battery compartment of the submarine.