'The inquiry has established that a member of the crew, a sailor, set off the anti-fire system on board the submarine, without authorisation and for no reason,' panel spokesman Vladimir Markin was quoted as saying.

'This sailor has already admitted his error,' RIA-Novosti quoted him as adding.

Twenty people were killed on Saturday when the fire extinguishing system was triggered as the new Akula-class nuclear-powered attack submarine was being tested in the Sea of Japan, pumping Freon gas into the vessel and depriving them of oxygen.

The authorities said there was no fire on board the vessel. -- AFP