Daily beach patrols will begin in Coromandel on Wednesday because it's feared that oil globules coming ashore in Tauranga from a grounded container ship could spread north.
The Rena has been wedged on Astrolabe Reef off the coast of Tauranga since 5 October.
The Waikato Regional Council says oil has washed up as far north as Matakana Island, 10km south of Coromandel.
The council's oil spill on-scene commander, Adam Munro, says three of the southernmost Coromandel beaches were checked on Tuesday but no oil was discovered.
Mr Munro is asking anyone who discovers oil on the beach to notify local authorities and action plans are in place.