Reports of a white plume observed in the water near the Rena wreck have been investigated by the Bay of Plenty Regional Council.
The regional council said in an advisory that about 3pm yesterday, staff were notified of a possible event on Astrolabe Reef, also known as Otaiti.
"Staff were told a white plume had been observed in the water near the reef, however, adverse weather conditions at the time hampered further investigation."
A flight over the reef this morning found there was no obvious white plume or discharge present.
"The regional council compliance team remain on standby and are continuing to follow up this report with residents on Motiti Island."
No further information was available.
Sunair aircraft pilot Dan Power said he flew over the Rena wreck about 10.30am this morning and "did not see anything".
He said it was a clear day on the reef but there was "nothing at all" near the wreck.
Buddy Mikaere, who represents Ngāi Te Hapū from Motiti Island, said he received a call yesterday from an "upset" friend on the island who said a large white "mushroom cloud" plume was seen floating roughly where the wreck lay.
He said if a leak had occurred, it was one of their "biggest fears" about "dumping their wreck on our reef".
It was hard to speculate what the plume might be but in his view, if a leak had occurred it was a sign the wreck could be starting to break up completely.
"It [the plume] could be a long list of things and if it's a toxin, it is going to affect the reef extremely badly."
He said if there was a toxic leak, he believed the impact on the environment would be terrible and the area's sea life could be polluted and unsafe to consume.
"This has always been our major worry."
The people of Motiti Island already avoided fishing on the northern side due to the wreck being nearby.
The Kaitiaki Reference Group, made up of local iwi, Bay of Plenty Regional Council and representatives of the Rena owners was set up to ensure the wreck would not cause harm, Mikaere said.
He said in his view this was showed the group was not working.
He said they had been assured the group would monitor the situation so leaks could not happen.
A spokesman for Rena's owner and insurer, Hugo Shanahan, refuted this claim, saying two invites had been sent to Ngati Hapu to put a person forward and the group was fully established.
He said the appropriate people were looking into reports of a white plume and he had also asked local fishing charters to check around the reef for any unusual signs.
He said a plane had flown over the area this morning and confirmed there was no sign of a plume near the wreck.
Shanahan said in his view it was disappointing the claims had been made before proper checks had been carried out.
"Astrolabe Reef is one of the most studied reefs in New Zealand and all the monitoring confirms it is recovering naturally and there is an extensive monitoring programme in place ... through the Environment Court," he said.
In 2017, the Environment Court ruled that the wreck of the Rena would be allowed to remain on Astrolabe Reef as everything that could be done had been done.
Te Atarangi Sayers, technical adviser for Motiti Rohemoana Trust which represented Motiti Island residents during the five-year legal proceedings regarding the Rena wreck, said the situation was, in his opinion, a potentially "tragic event" and he was still learning more.
"We are extremely concerned with potential impact to our pataka kaimoana and the mauri of the Motiti rohe being further affected."
It is understood the white plume had reached the northern shores of Motiti Island.