No oil leaks have been found the area where the NZ Navy ship HMNZS Manawanui sank yet, the Samoa government says.
The Ministry of Works chief executive Fui Mau Simanu told RNZ Pacific that New Zealand Navy divers had been assessing the area since Tuesday morning.
He said they were working alongside local police and Samoa's Natural Resources and Environment Ministry.
"We haven't seen any leakage or any sort of spillage," Fui said.
"But we should have a fair idea of any damage to the environment if there is any probably tonight, when the teams come back from their assessment," Fui said.
Read more:
The Royal New Zealand Navy vessel ran aground south of Upolu on Saturday night as it was conducting a reef survey.
Chief of Navy, rear admiral Garin Golding told Morning Report nearly 1000 tonnes of diesel fuel was onboard HMNZS Manawanui when it sank.
Fui said the risk of an oil spill poses the biggest environmental risk, with some reports of oil already leaking.
"I can't confirm anything there's some speculation [of a leak] but we will have a true assessment hopefully tonight when the teams come back," Fui said.
He said the weather had improved since Monday which meant the assessment teams were able to be fully mobilised.
University of Waikato's Professor Chris Batter said the effect of ship hulls on coral reef systems can be quite damaging.
"Because a lot of the antifouling paint comes off and gets ground into the corals. Where that can be cleaned up, then recovery of the corals can happen quite quickly.
"If it's left there, particularly if it's some of the older style anti-fouling paints that have tin in them, the effects can be quite long-lasting," Professor Batter, who is the chair of the Coastal Science, said.
'We are concerned' - conservation society
Samoa Conservation Society coordinator Ioane Etuale said the organisation did not see any oil at the three sites they visited close to the ship.
"We saw regular clean water and clean sand, there were no signs of any oil residues or [oil] washed up to the shores," he said.
However, Etuale said he was told by a local fisherman oil washed up on the beach Sunday and they had seen a number of dead turtles early Monday morning.
"This type of threat is new to Samoa, I don't think it happens often, so I am not sure how well equipped we are to respond to such incidents," Etuale said.
"We are concerned, we want to know what what's in that boat, it needs to be looked at."
Brent Ross, who is the owner of Offshore Adventures, a surf tour business, travelled on his boat close to the site of where the boat sank and said he saw both diesel and rubbish in the water.
He said about half-a-mile west of where the boat sunk he saw what looked like food containers, one of them was broken letting out food.
"There were food products spilling everywhere," he said.
"There was a lot of what I took to be diesel fuel on the water it was quite bad."
Ross said he picked up lifejackets and bits of timber from the ship.
He checked one of the regular surf spots he takes clients to and said rubbish was flowing through the line-up.
"A lot of people come all over the world predominantly to surf one or two of these waves over here," he said.
"They are world class waves and when I had a look at it there was just fuel flowing through the line-up, rubbish everywhere. I can't put people out in that.
"If I can't take people out snorkelling surfing and fishing do I have a livelihood?"
Ross said his guests at the moment were understanding of the situation but hoped everyone would do as much as they could to stay on top of the situation.
