Manawanui, the navy’s specialist dive and hydrographic vessel, ran aground near the southern coast of Upolu on Saturday as it was conducting a reef survey, Commodore Shane Arndell, the maritime component commander of the NZDF, said.

Several vessels responded and assisted in rescuing the crew and passengers who had left the ship in lifeboats, Arndell said.

Those rescued “are being supported in Samoa or on supporting vessels,” he said. The NZDF had earlier said there were 78 passengers and crew aboard the ship.

A Royal New Zealand Air Force P-8A Poseidon was also deployed to assist in the rescue.

The cause of the grounding was unknown and would need further investigation, the NZDF said.

Video and photos published on local media showed the Manawanui, which cost the New Zealand government NZ$103 million (US$63.4 million) in 2018, listing heavily and with plumes of thick grey smoke rising after it ran aground.

The vessel later capsized and was below the surface by 9am local time, the NZDF said.

The agency said it was “working with authorities to understand the implications and minimise the environmental impacts”.

Rescue operations are being coordinated by Samoan emergency services and Australian defence personnel with the assistance of the New Zealand rescue centre, according to a statement from Samoa police, prison and corrections service posted on Facebook.

Manawanui was used to conduct a range of specialist diving, salvage and survey tasks around New Zealand and across the Southwest Pacific.

The New Zealand navy is already working at reduced capacity with three of its nine ships idle due to personnel shortages.