Officials from the Japanese Maritime Self-Defense Force (MSDF) said that one of their submarines that collided with a commercial vessel off the western coast of the country has been damaged more than initially thought.

The officials said on Tuesday that the 84-metre-long Soryu Class submarine sustained damage to its conning tower and its hydroplane due to the collision in the Pacific Ocean, off the main island of Shikoku.

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The submarine’s communications equipment also sustained damaged, which led to a three-hour delay to report the incident.

Chief Cabinet Secretary Katsunobu Kato told a press briefing on Tuesday that steps should be taken by the MSDF to ensure that such communications delays do not occur again.

MSDF Chief of Staff Adm. Hiroshi Yamamura offered his apologies and said the communications delay was inexcusable.

Defence Minister Nobuo Kishi has also apologized for the incident in which three crew members on the submarine were injured.

On Monday, Kishi said that despite the commercial vessel being visible in the submarine’s periscope, it was unable to avoid the collision.

But, according to informed sources within the Defence Ministry, the collision may have been a result of human error on the MSDF’s part, with personnel on the submarine failing to properly check the surroundings using sonar before surfacing.

Kishi also said that the Japan Coast Guard has launched a probe with the full cooperation of the MSDF and the Defense Ministry.

Transport Minister Kazuyoshi Akaba has confirmed that no one aboard the commercial vessel was injured and it was able to navigate away without any problem.

He also said the Japan Transport Safety Board will conduct an independent investigation into the incident.