Bay of Plenty Regional Council is investigating how hundreds of tyres were dumped in forestry blocks near Rotorua.
The Taranaki and Waikato regional councils are investigating a spate of similar dumpings.
Hundreds of tyres in piles were found in two parts of Mamaku Forest and another private property closer to Rotorua in mid-May.
On June 15, Waikato Regional Council received a report of a "couple of hundred" tyres being dumped in a quarry off State Highway 5, Tirohanga.
On July 6, the Waikato Regional Council was contacted by a forest management company advising of five new piles of dumped tyres discovered in one of their forest blocks.