Two Russian tankers carrying mazut, a low-quality heavy fuel oil with a wide range of industrial applications, in the Black Sea’s Kerch Strait have sent distress signals after one vessel ran aground, the Russian Emergency Situations Ministry told Russian business daily RBC on Sunday.

Screenshot: Mash Telegram channel

Volgoneft-212 and Volgoneft-239, carrying a total of 29 crew members according to state news agency TASS, “sustained damage” due to “difficult weather conditions”, the ministry said, adding that while one of the tankers had run aground, the second was “drifting”.

According to state-affiliated news agency Interfax, the Volgoneft-212 was carrying about 4.3 thousand tonnes of fuel oil. The amount of fuel oil being carried by the Volgoneft-239 has not been disclosed.

Both tankers are rapidly sinking, according to videos posted by Telegram channel Mash, while a video shared by the Crimean Wind Telegram channel appears to show Volgoneft-212 being broken in two by strong waves. While rescue efforts to pull out sailors out of the water were ongoing, “a huge black spot” appeared in the water around the vessels, Mash added.

A source involved in the rescue effort told Interfax that there was still “no exact information” on the volume of oil products that had spilled into the water.

According to Mash, 10 sailors have been rescued so far, while at least another 13 are still in the water. At least four, who could have been in the engine room or in the hold at the time of the crash, are unaccounted for, Interfax reported.