"The Scientific Research Organization of Samoa has submitted a comprehensive plan for testing seawater and marine species near the wreck site to monitor and determine any contamination within the affected area."
The New Zealand Defence Force said removing fuel will be its priority, and its teams on the ground are focused on protecting the environment.
Precautionary Zone map [Photo: Supplied]
Commodore Andrew Brown said a dive team from HMNZS Matataua would be involved in underwater surveillance of the ship.
He said coastal areas were also being monitored.
Residents in the affected areas are being urged by MPAC to report any debris, diesel slicks, or signs of impacted marine life.
Nick Ling, from the University of Waikato's School of Science, said any decision about removing the wreck itself was a "very complex decision process", given the potential cost, difficulties in achieving its removal considering where it lies adjacent to the reef and in a relatively exposed location; and the wishes of local people and the Samoan Government.
"Removing the wreck entirely would be extremely challenging given the lack of infrastructure to deal with the salvaged wreck in Samoa or anywhere nearby."
He said there was potential for the Manawanui to be left there as a dive site.
"Although that would depend on whether the ship lies in a sufficiently sheltered location to survive long-term exposure to heavy seas.
"While many old warships are purposely sunk as dive sites or for the purposes of forming an artificial reef, they are rigorously decontaminated first.
"In its current state the wreck itself poses relatively little threat to the reef once the fuel and other potential contaminants are removed, but if it were to break up then it could cause considerable additional physical damage to the structure of the reef."
Ling said the NZDF had reported that ongoing monitoring of the wreck and surrounding coastal area is continuing, "but it is unclear whether this relates simply to the presence of debris and oil".
"I would have thought the NZ Government owed it to the people of Samoa to undertake whatever work was required to allay fears of the potential or current impacts of the wreck."
At the Commonwealth Heads of Government meeting, deputy Prime Minister Winston Peters said New Zealand should not apologise to Samoa for the environmental impact from the HMNZS Manawanui sinking and ongoing fuel leaks.
However, Prime Minister Christopher Luxon said last month he had consistently conveyed New Zealand's apologies for the unfortunate accident to Samoan Prime Minister Fiamē Naomi Mata'afa, including on his trip to the East Asia Summit in Laos.
"Consistently conveyed that we are sorry this unfortunate accident happened, but what we are very focused on as a combined New Zealand-Samoa team is actually making sure we stay very very focused on the task at hand."