Russian authorities are investigating an explosion early Sunday in the engine room of an oil tanker thought to be linked to the Kremlin’s “Shadow Fleet” of merchant vessels that attempt to skirt international sanctions against Moscow.

According to Russian media reports, the explosion occurred in the engine room of the Koala while it was docked at the port of Ust-Luga near St. Petersburg.

The Russian news Telegram channel Baza, thought to be close to the country’s security services, said the Koala was carrying 130,000 tons of fuel oil and was in danger of sinking. The ship had 24 crew members — a mix of Russians, Georgians and Indonesians. It is listed as being registered to Antigua and Barbuda.

“The vessel was already preparing to sail when three powerful explosions thundered in the engine room,” Baza reported on its Telegram page.”The crew managed to get ashore, but the ship’s engine room began to flood with water.”

Russian authorities said the crew members weren’t injured, and there was no fuel leak. However, booms have been placed around the ship to prevent any possible spillage from contaminating the water.

Officials in nearby Finland aren’t taking any chances. The country’s prime minister said his government is “closely following” the news about the damaged oil tanker.

“Finnish authorities are investigating the situation. Finland has increased its oil spill response readiness,” Prime Minister Petteri Orpo posted Sunday on X.

Ukraine has struck targets in Russia’s critical port along the Baltic Sea, but it wasn’t immediately clear Monday if Kyiv was involved in the explosion on the Koala.

• Mike Glenn can be reached at mglenn@washingtontimes.com.