Volunteers and Northland Regional Council staff have scooped up more than 100 litres of heavy, sticky oil washed ashore on two Far North beaches since Sunday.
About 80 litres was cleaned up by the council staff after it came ashore at Matai Bay, on the Karikari Peninsula northeastof Kaitaia, in flat sticky globules up to the size of a dinner plate.
Smaller amounts turned up yesterday on nearby Tokerau Beach, where another 20 litres was collected.
Regional council harbourmaster Ian Niblock said the oil appeared to have been in the sea for several days and its consistency in the water made recovery by council staff relatively easy.
It was possible, however, that oil could continue to wash ashore in the wider Cape Karikari area for several days and staff were checking two other beaches further north on the Aupouri Peninsula after yesterday's high tides.
By last night, small amounts of oil had been found washing ashore along a stretch of the Far North's east coast from Doubtless Bay to the entrance of Parengarenga Harbour, just below North Cape.
Mr Niblock said the type of oil, the way it had come ashore and the relative ease of recovery meant it was unlikely there would be any lasting environmental damage to the beaches, although the situation would be closely monitored.
The source of the spill has yet to be determined but is thought most likely to have come from a contaminated bilge-water discharge from a cargo ship.
Oil samples have been collected for analysis and the council will try to track down the vessel responsible.
Meanwhile, the council is warning people to take care when walking along east coast high tide lines on beaches in the area.
People finding what they suspect is oil should contact the regional council's 24-hour environmental hotline on freephone 0800 504-639.
