New details surrounding the sinking of the Russian cargo ship Ursa Major in December 2024 have led to speculation that it was transporting submarine nuclear reactor parts meant for North Korea. Spanish authorities, along with reports from CNN and the newspaper La Verdad, indicate the ship’s last voyage involved sensitive cargo connected to Russia’s military.

The Russian-flagged ship sank just before midnight on December 23, 2024, about 71 miles off the southeastern coast of Spain near Murcia, after several explosions were reported on board. The 467-foot vessel was owned by Oboronlogistics, a company connected to the Russian government and defense logistics.

Distress call followed by mysterious explosions

Spain’s maritime rescue agency, Sasemar, responded when the Ursa Major sent a distress signal at 12:53 p.m. local time. Rescue teams sent a helicopter, a tugboat, and a fast-response boat after nearby ships observed the cargo vessel slow sharply and tilt to one side.

Crew members later told rescuers that three explosions had happened in the engine room. As the situation got worse, several sailors left the ship.

Spanish rescue teams reportedly changed their plans later that evening when a Russian warship arrived at about 8:07 p.m. A Spanish government document released earlier this year said the Russian military ship took over and told Spanish rescue boats to stay at least two nautical miles away.

The same report stated that the Russian warship fired flares over the damaged ship. According to La Verdad, the flares might have been used to block infrared surveillance satellites watching the scene.

CNN later reported that investigators detected “four similar seismic signatures … the pattern of which resembled underwater mines or overground quarry blasts” shortly after the flares were deployed. By 11:20 p.m., the Ursa Major had sunk in waters about 8,200 feet deep. Fourteen crew members survived, but two are believed to have died in the first explosions.

Suspicious cargo raises concerns

Russian officials first said the ship was carrying “non-dangerous merchandise,” such as shipping containers, cranes, and two large maintenance hole covers. However, Spanish investigators reportedly grew suspicious after looking at satellite images that showed two large blue cargo containers near the back of the ship. Each container was estimated to weigh about 72 tons.

During questioning, the ship’s captain reportedly admitted that the so-called “manhole covers” were actually “nuclear reactor components similar to those used by submarines,” but said there was no nuclear fuel on board. Investigators reportedly questioned why such large cargo would be shipped over 9,300 miles by sea from St. Petersburg to Vladivostok instead of being transported by land through Central Asia.

“These would therefore be two loads almost impossible to transport along the winding roads of Russia, Kazakhstan, Uzbekistan, and Afghanistan between the two cities served by the Ursa Major,” said the report in La Verdad. “That mysterious undeclared cargo would certainly justify a voyage of more than 15,000 km (around 9,320 miles) by sea between St Petersburg and Vladivostok.”

According to CNN, a source familiar with the investigation claimed the ship’s captain believed the cargo would ultimately be redirected to the North Korean port city of Rason.

Torpedo theory adds to mystery

The investigation has also raised questions about possible sabotage. CNN and La Verdad reported that investigators discovered a 20-inch-by-20-inch hole in the ship’s hull, with metal bent inward, suggesting an external impact.

The reports mentioned the possibility of a supercavitating torpedo, a fast underwater weapon that moves more easily by surrounding itself with gas bubbles.

“Only the United States, a few Nato allies, Russia, and Iran are believed to have this kind of high-speed torpedo, which fires air ahead of the weapon to reduce the drag of the water,” stated CNN. “The source familiar with the [Spanish] investigation said it concluded the use of such a device would fit with the size of the hole in the Ursa Major’s hull, and that it could have made a noiseless impact resulting in the sudden slowing of the boat on 22 December.”

CNN also reported more military activity near the wreck site over the past year. This included flights by US nuclear detection planes and more explosions caused by a Russian spy ship days after the sinking.

Oboronlogistics has called the incident “a targeted terrorist attack.” Spanish authorities have not said publicly what caused the sinking.