Maritime New Zealand can't find any sign of an oil spill off the Taranaki coast.

A flight with Maritime NZ (MNZ) observers on board this morning couldn't find any signs of an oil sheen following the spill from the floating oil storage facility Raroa, on Friday.

MNZ confirmed today it was investigating a spill from the Raroa, the third at the site in less than five years.

The Raroa, a converted oil tanker is 250 metres long and 40m wide, has been operating in the Maari Field - located in the South Taranaki Bight about 80 kilometres off the coast - since 2008.

Peter Zeilinger, managing director of OMV New Zealand Ltd, which runs the operation, said a small spill occurred when oil from the Raroa was being transferred to the tanker Nectar.

"The transfer hose developed a leak close to the connection point on board the Nectar and oil spilled onto its deck," Zeilinger said.

"The majority of the spill was recovered on board the tanker and transferred to its cargo tanks but a small amount, estimated to be less than 2 barrels [300 litres], entered the sea."

Loading operations were halted immediately and the incident was reported to MNZ, Zeilinger said.

Cleanup operations began straight away and a tracking device was launched with the oil sheen, he said.

"Helicopter flights with trained observers monitored the sheen over the weekend," he said.

"It began to break up and diminish naturally, and a further flight this morning with Maritime New Zealand personnel on board was unable to detect any trace of the spill."

OMV NZ had halted offtake operations until repairs had been undertaken, he said.

Zeilinger said the spill was regrettable and OMV, together with MNZ, would conduct a full investigation.

Taranaki Regional Council director resource management Fred McLay said the council was notified but the incident occurred outside the council's 12-mile (20-kilometre) limit and the Environmental Protection Authority and MNZ were the regulatory authorities.

In 2010 two oil spills were reported at the Maari Field in a little more than a month - one on October 18 and another on November 20.