A fire that broke out on a Russian nuclear submarine at an Arctic naval shipyard has been put out, Russian media report.
The blaze on the Orel began at a Severodvinsk shipyard during repairs.
There were no weapons or nuclear fuel on board the Oscar-II class vessel at the time of the incident and there were no reports of any casualties.
A shipyard's spokesman said that no environmental or radioactive contamination had occurred.
The Russian Investigative Committee has announced that it is launching an investigation into alleged safety violations that could have started the blaze during the repairs.
"The source of the smoke on the submarine Orel, which is undergoing a refit at Zvezdochka [shipyard], has been completely put out," said shipyard spokesman Yevgeny Gladyshev, quoted by Interfax news agency.
"Smoke is no longer coming out, only steam."
He added that the vessel's dock had been submerged in water in order to put out the fire and that the submarine's hull was still being doused in water from above.
Earlier, Mr Gladyshev told Tass news agency that the water would not cause any damage to the equipment inside the submarine because the inner hull remained closed.
A spokesman for the corporation which runs the shipyard, Ilya Zhitomirsky, told the Associated Press news agency that the critical parts of the submarine's nuclear reactor had been removed long before the repair work had begun.
The Orel submarine joined the Northern Fleet's base in Murmansk region in 1992, reports say, and on operations it is armed with anti-ship missiles.
It was moved for repairs to Severodvinsk, a city near Arkhangelsk on the White Sea, in 2013.
Local media said that the blaze on the 155m-long (500ft) submarine began when some insulation material caught fire during welding work.
In 2011, the Yekaterinburg nuclear submarine was damaged in a huge fire during repairs in the northern Murmansk region.
Nine people were hurt fighting the blaze that started after the submarine's rubber-coated outer hull caught fire.