An estimated 200 to 300 litres of lubricating oil has been spilt in Akaroa Harbour by the anchored Royal New Zealand Navy vessel HMNZS Te Kaha.
Environment Canterbury said it was notified of the incident immediately by the New Zealand Defence Force.
"We’re now working alongside them to monitor and support clean up efforts."
A New Zealand Defence Force spokesperson told 1News that immediate steps were taken to clean up the approximately 200-300 litres of lubrication oil from the 118m long vessel.
Soaker pads were used to clean up surface oil and oil dispersed by crew on a RHIB following the leak, which was caused by a defect to an oil cooler on the starboard engine," they said in a statement.
"The source of the leak has been isolated and no further oil is leaking."
The ship remained anchored in Akaroa Harbour, NZDF said.
The ship's company was working with Environment Canterbury staff who are monitoring and assisting with clean-up efforts.
How 300L of lubricating oil differs from diesel oil
Environment Canterbury Regional on-scene commander Emma Parr told 1News the group's focus was on "minimising environmental impacts".
"In this case, we're working with the New Zealand Defence Force, Maritime New Zealand, our local partners and stakeholders, to assess the impacts and coordinate the on-water response to contain and recover the oil," she said.
She said the type of persistent oil — which was a thicker and heavier oil — would smother the environment rather than naturally disperse, and required a "physical intervention".
"Many of our recent spills have been diesel oil, which is a lighter oil, and it disperses really well naturally with tidal changes and weather.
"This persistent oil needs physical intervention. So it needs us to be out there using tools and equipment to contain it and recover it from the surface of the water," she explained.
Environment Canterbury Regional on-scene commander Emma Parr. (Source: 1News)
"It's not a large volume, but the type of the oil means that it will have a potentially higher environmental impact, because it is so thick.
She said the containment and recovery method used had been "showing really good effectiveness throughout the day".
She encouraged anyone who had seen wildlife impacted by oil to get in touch with Environment Canterbury on 0800 765 588, and avoid the area.
Local resident Mark Robinson told 1News a visible oil slick was heading towards the Wainui side of the harbour.
In late January, a tourist boat ran aground near the mouth of Akaroa Harbour, resulting in 2240 litres of marine diesel fuel and 120 litres of other oils being leaked into the sea.
