Smoke rises over the Russian Oscar II-class nuclear-powered submarine Oryol at the Zvyozdochka shipyard in Severodvinsk, Russia, April 7, 2015. [Photo/IC]

MOSCOW - A Russian nuclear submarine caught fire Tuesday while undergoing maintenance at the Zvyozdochka shipyard in the northern Arkhangelsk region. No casualties were reported.

The United Shipbuilding Corporation, which manages the facility, said the crew has been evacuated with none wounded.

Shipyard spokesman Yevgeny Gladyshev said the fire may have been caused by violations of welding regulations.

"As a result of violations of the technological process during the welding work, a fire broke out in the lower part of the hull," the Interfax news agency quoted him as saying.

There were no weapons or nuclear fuel on board when the fire broke out, Gladyshev added.

The fire has been localized and firefighters are trying to fill the dock with more water in order to extinguish the fire, which is expected to last for two more hours, said Gladyshev.

The Kremlin spokesman Dmitry Peskov said President Vladimir Putin has been updated on the incident, and it was just too early to draw any conclusion about the cause.

In response to public concerns that the incident may cause broader damage, the Russian Investigative Committee said " preliminary data suggest that the incident poses no danger to public safety and health and no danger to the environment," and that local investigators have launched a criminal case over the fire.

The submarine is identified as the 949A Oryol nuclear submarine, which is equipped with two reactors and classified as Oscar-II by the North Atlantic Treaty Organization (NATO).

A similar incident happened in 2011 when the Yekaterinburg nuclear submarine caught fire at a shipyard in Russia's northern city of Murmansk, injuring nine firemen who were being poisoned by smoke when trying to extinguish the fire.