A special commission has concluded that a blast accident onboard a Russian submarine last Sunday was caused by a mechanical failure, a high-ranking official was quotedby Interfax as saying on Saturday.

The explosion, which occurred onboard the second-generation submarine belonging to Russia's Pacific Fleet, killed sailor Dmitry Koval and injured several other servicemen, said the official.

"The commission has concluded the accident onboard the K-223 nuclear submarine was due to a mechanical problem. The explosion onboard the submarine was caused by a rupture of a pipeline providing pressure to a fresh water tank," the official said.

He said that the conclusions have been reported to the Navy commander and the defense minister.

The accident took place when the submarine was at its base in Kamchatka, according to him.

A source with the Pacific Fleet headquarters said earlier that the fleet's military prosecutor's office had initiated a criminal investigation into the sailor's death.

Source: Xinhua