The Russian military firefighters have extinguished a fire on the exterior of a nuclear submarine docked in a northern Russia shipyard, and there has been no radiation leak.

An official said Friday an undisclosed number of crew members inside theYekaterinburg nuclear submarine were in no danger while it was burning.

The official says they were monitoring temperatures and carbon dioxide levels inside the vessel to ensure its safety.

The military at least seven people, including firefighters have been taken to the hospital for smoke inhalation after the fire erupted Thursday.

The fire happened while the vessel was docked for repairs in the northern Murmansk region.

The Russian Defense Ministry said all of the submarine's weapons had been unloaded before the repairs and its reactor had already been shut down. The Delta IV class vessel is able to carry 16 intercontinental ballistic missiles.

Video footage showed large clouds of smoke rising from the area. The blaze is believed to have started on the wooden scaffolding at the shipyard.

Officials say the fire is under investigation.

In August 2000, Russia's Kursk nuclear submarine sank at sea, killing all 118 crew members on board.