The 14 sailors who died in a submarine fire earlier this month in the Barents Sea could have survived, if they’d abandoned ship sooner, but they stayed behind to fight the blaze, sources told the newspaper Kommersant. According to Russian defense officials, the officers died trying to put out a fire in the battery compartment of a deep-water research ship that was performing bathymetric measurements.

The submarine’s crew reportedly acted in strict accordance with the navy’s damage-control policy, which requires sailors to fight any fire in the part of the ship where they are stationed. If a sailor leaves his post without direct orders, he faces possible criminal prosecution.

Kommersant’s sources say the fire may have started due to problems in the submarine’s electrical system. After smoke started leaking from the battery compartment, six sailors left the ship, while another 10 remained on board. The ship’s commander, Captain Konstantin Somov, requested permission to evacuate when his crew ran out of breathing equipment and several sailors started passing out. Four hydronauts arrived to help the remaining crew evacuate the ship, but an explosion killed everyone, including the 10 sailors and four rescuers.

A commission investigating the fire is reviewing three possible explanations for the disaster: equipment failure, crew error, and malicious attack, writes Kommersant, confirming reports by the website Fontanka that the fire may have started because of a lithium-battery explosion.

According to news reports, the submarine relied on lithium-ion batteries manufactured by the Russian company “Rigel,” which were installed to replace silver-zinc batteries previously supplied by a Ukrainian contractor. In company documents reviewed by journalists, Rigel claimed to have tested its batteries for explosion safety.

For more about this tragedy A high-ranking crew in a shallow sea We asked Russian military experts to explain the Barents Sea submarine fire