Oil company OMV New Zealand is apologising for causing two oil spills in just over a month and says it is working to minimise any environmental risk.

The company is part of the global OMV Group, based in Austria, and operates the Maari oil field 80km off the Taranaki Coast.

The Raroa floating production storage and offloading vessel is permanently moored at Maari and was the source of both leaks - one on Saturday and one on October 18.

OMV New Zealand managing director Dr Wayne Kirk said today a thin sheen was seen off the Raroa on Saturday and Maritime New Zealand (MNZ) was notified immediately.

"OMV mobilised a helicopter to fly over the area with a trained observer. No oil was visible on the water. It is believed that the amount of oil leaked was very small, but work is still being done to confirm the actual volume," Dr Kirk said.

"It is expected that the oil will continue to break down naturally. OMV will continue to monitor the situation carefully and remains prepared to support MNZ should the situation change."

Production on the Raroa had been reduced while the source of leak was found.

On October 18, oil was also noticed on the water near the Raroa, the operation stopped and MNZ notified. A flight over the area within two hours of the leak showed no sign of the oil but globules were seen on several Kapiti Coast beaches last week.

"While the source of that oil is still unknown, we've taken a prudent approach. Even though independent experts have indicated the environmental impact of the small oil globules is low, we organised a clean up of the area with OMV and Tanker Pacific staff volunteers," Dr Kirk said.

"This was started on Friday and completed Saturday."

Staff would continue to monitor Kapiti Coast beaches over the next week, and samples would by analysed to determine whether the oil was from Maari.

"OMV - both worldwide and here in New Zealand - has a very good environmental track record and we take any release of oil into the environment very seriously," Dr Kirk said.

"OMV sincerely regrets the recent incidents on the Raroa. We're committed to working closely with Tanker Pacific to ensure best practices are followed to minimise any environmental risks."

Production on the Raroa had been reduced while the source of leak was found.