MOSCOW, August 1 (RIA Novosti) - A fire inside a nuclear submarine being dismantled at a plant in Severodvinsk was caused by diesel vapor igniting, chief engineer of the plant Oleg Frolov said Monday.

The Victor class submarine, which was built at the end of the 1970s, was decommissioned in 2004, and sent to the shipyard for dismantling, the company press service said.

The fire broke out at 08:30 Moscow time (04:30 GMT) on Monday in the Zvezdochka company's plant in Severodvinsk when fuel vapors ignited during work to cut up the vessel.

One person was killed in the accident and another is being treated for burns. The fire has been extinguished.