In this Sunday, July 27, 2014 photo Russian President Vladimir Putin, left, watches a nuclear submarine of the Northern Fleet to mark the country's Navy Day in Severomorsk, Russia.
FILE - Russian President Vladimir Putin, left, watches a nuclear submarine off the Northern Fleet to mark the country's Navy Day in Severomorsk, Russia, July 27, 2014.

Fourteen sailors have died in a fire on a deep-sea submersible, the Russian military says.

The fire broke out Monday while the crew was in Russian territorial waters, gathering biometric measurements for a military survey, according to the Defense Ministry.

The seamen died of smoke inhalation. The submersible is now at the arctic port of Severomorsk, the Russian northern fleet’s main base in the Barents Sea.

Map of Severomorsk Russia

An official investigation is underway.

The northern fleet faced another loss in August 2000, when a nuclear-powered submarine was damaged by two explosions in its bow and sank. All 118 men aboard died.

While submarines are fully autonomous, submersibles usually require support ships on the surface.