The Oscar II class Orel submarine caught fire earlier in the day during a scheduled overhaul in a dry dock at the shipyard. The total area of the fire is estimated at about 40 square meters (1.5 square miles).
"Today, as a result of violations of the technical process during the welding works, a fire was ignited in the lower part of the hull of the Orel submarine, which is undergoing planned overhaul at the Zvezdochka shipyard," Yevgeny Gladyshev said.
Gladyshev stressed that the situation at the site of the incident had been under full control of the shipyard authorities.
The Investigative Committee launched a criminal investigation into the blaze, which did not result in casualties and does not appear to threaten nearby vessels.
Authorities started extinguishing the fire on board the Orel by filling the dry dock with water through its partial submersion 7 hours after the flames broke out. Previously, firefighters have put out traces of open fire by filling foam in spaces between the hulls of the boat, where heavy smoke continued to be observed at the site of the outbreak.
The United Shipbuilding Corporation's spokesman later assessed the flames would be put out "in the coming minutes" as water rising in the docks began reaching required levels.