Norway has found a radiation level 800,000 times higher than normal at the wreck of a Russian navy submarine.
The Komsomolets sank in the Norwegian Sea in 1989 after a fire on board killed 42 sailors.
A sample showed radioactive caesium leaking from a ventilation pipe, but researchers said it was “not alarming”, as the Arctic water quickly diluted it.
The Soviet-era sub is also deep down, at 1,680m (5,512ft), and there are few fish in the area, they added.
For the first time a Norwegian remotely-operated vehicle (ROV) examined and filmed the Komsomolets on 7 July, revealing severe damage.
The submarine is also known as K-278 in Russia, and it sank carrying two nuclear torpedoes with plutonium warheads.
The news comes just over a week after fire swept through a Russian nuclear-powered submersible in the Barents Sea, killing 14 naval officers.
The survivors managed to get the mini-sub back to its Arctic base.
Norway’s Radiation and Nuclear Safety Authority (DSA) says the pressurised water reactor powering K-278 in April 1989 shut down quickly when the fire broke out in another compartment.
Twenty-seven sailors survived – they were eventually picked up by two Soviet ships.