The captain of a Japanese fishing boat was referred to prosecutors Tuesday over the deaths of three crew members following a collision with a Russian ship off the northernmost main island of Hokkaido last month, the Japan Coast Guard said.

Teruyoshi Yoshioka, the 63-year-old captain of the Hokko Maru No. 8 crewed by five, is suspected of professional negligence resulting in death, as well as endangering traffic due to negligence, over the failure to avoid a collision with the 662-ton Russian ship Amur on May 26, according to the Mombetsu Coast Guard Office.

Photo taken from a Kyodo News helicopter on May 26, 2021, shows a capsized Japanese fishing boat, the Hokko Maru No. 8, drifting about 20 kilometers northeast of Mombetsu in Hokkaido after colliding with Russian vessel Amur. (Kyodo)

The crew members aboard the 9.7-ton Japanese boat, belonging to a fishery cooperative based in Mombetsu, Hokkaido, were catching hairy crabs when the collision occurred around 6:30 a.m.

Yoshioka allegedly failed to sufficiently check the boat's radar despite navigating in low visibility due to dense fog, causing three crew members to fall into the sea and drown when it collided with the Russian vessel and capsized.

Pavel Dobrianskii, 38, a third officer who was in charge of the Amur at the time of the collision, was sent to prosecutors by the coast guard Tuesday on the same charges following his arrest the previous day.

The Russian vessel with 23 crew members aboard was transporting seafood to Mombetsu from Sakhalin in the Russian Far East.

The Mombetsu coast guard said it believes Dobrianskii was liable after it found during voluntarily questioning that the 46-year-old captain of the Amur had not been involved in the operation of the ship at the time.

Deckhands on the Amur saw the Hokko Maru just before the collision, but there was no time to take evasive maneuvers. The Hokko Maru also did not notice the Amur until it was too late, according to the coast guard.

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