A Russian cargo ship, Ursa Major, sank in the Mediterranean overnight after a massive explosion occurred in its engine room, Reuters reported on Tuesday, citing the Russian Foreign Ministry.

The State Department also confirmed that 14 of 16 crew members were safely rescued and taken to the Spanish port of Cartagena, but two crew members remained missing.

The reason for the engine explosion has not been disclosed and is currently under investigation. According to the Russian Embassy in Spain, state news agency RIA Novosti said it was investigating the accident and was in contact with local authorities.

The Spanish maritime rescue service reported receiving a distress signal from the Ursa Major on Monday. A nearby ship confirmed that there were poor weather conditions, a lifeboat was in the water and Ursa Major was listing to starboard.

Two ships and a helicopter were dispatched to the scene. The crew said the ship was carrying empty containers and two port cranes on deck.

A Russian warship later arrived at the scene of the accident and took over the rescue operations.

The Ursa Major was Oboronlogistika’s largest cargo ship, with a capacity of 1,200 tons and capacity to transport 120 vehicles on deck.

According to Bloomberg, the company reports to the Russian Ministry of Defense and handles the transport of both military and civilian goods.

According to Bloomberg, the ship was recently repaired in November before it was scheduled to sail to the port of Vladivostok with heavy cargo.