A series of human errors caused a New Zealand navy ship to plough into a reef off the coast of Samoa, where it caught fire and sank, according to the preliminary findings of a military court of inquiry into the disaster.

The ship’s crew did not realise the autopilot was engaged, believed something else had gone wrong with the ship, and did not check that the HMNZS Manawanui was under manual control as it maintained course towards land, a summary of the inquiry’s first report published on Friday said. The full report has not been made public.

All 75 people on board the vessel evacuated safely as the boat foundered about a mile off the coast of Upolu, Samoa, in October. The ship was one of only nine in New Zealand’s navy and was the first the country lost at sea since the second world war.

Officials did not know the cause of the sinking at the time and Chief of Navy Rear Adm Garin Golding ordered a court of inquiry to investigate.

“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,” Golding said in a statement on Friday.

The crew “mistakenly believed its failure to respond to direction changes was the result of a thruster control failure,” he said. A number of contributing factors were identified, Golding said, although he did not say what they were.

The court of inquiry is expected to continue until the first quarter of next year. Golding said given human error was identified as the cause, a separate disciplinary process will begin after the inquiry.

“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,” Golding said.