• A New Zealand naval ship that capsized and sank off Samoa last month had been left on autopilot.
• That's according to a preliminary investigation that found the ship's crew made a series of errors.
• The vessel crashed into a reef and suffered "catastrophic" fires before sinking, it said.

A Royal New Zealand ship that capsized and sank off the coast of Samoa was left on autopilot, according to preliminary findings from a military court of inquiry.

Crew members lost control of the HMNZS Manawanui, which cost about $63 million, on October 5 while they were conducting a hydrographic survey off the coast of the island of Upolu.

"The direct cause of the grounding has been determined as a series of human errors, which meant the ship's autopilot was not disengaged when it should have been," Chief of Navy Rear Adm. Garin Golding said in a press statement on Friday.

Golding said the crew did not realize that the ship was still on autopilot and assumed that its failure to respond to changes of direction was due to a thruster control malfunction.

The crew tried to change course several times. However, the ship continued on its path until it struck a reef off the coast of Samoa at 10 knots, or roughly 11 miles per hour. It then traveled for another 635 meters until it became stranded, the statement said.

All 75 crew and passengers were evacuated 30 minutes after the initial grounding, and before the ship suffered a series of "catastrophic" fires and sank the next morning, it said, likely preventing serious injuries or death.

"To provide some immediate assurance," Golding said, "we have conducted a series of audits in the Fleet and looked to implement initial lessons identified from the interim report around training, risk management, and improving relevant orders, instructions, and procedures."

"I want to reassure the public of New Zealand that we will learn from this situation and that it is on me, as the Chief of Navy, to earn back your trust," he added.

A second phase of the inquiry will examine other contributing factors.

According to a series of updates on its website, New Zealand's Defence Forces has been working to remove and safely dispose of the fuel and pollutants from the ship.

New Zealand's Defence Forces didn't immediately respond to a request for comment.

The Manawanui, built in 2003, is a specialist dive and hydrographic ship mainly used for coastal and harbor surveys, underwater explosive disposal, and search and recovery operations.

It entered service with the Royal New Zealand Navy in 2019.