Fire crews have put out three large, suspicious fires in grass and scrub near the Northland town of Ruakaka.
Fire station officer Jeff D'Ath says there have been problems with arsonists in the area for the past 12 months.
Mr D'Ath says three fires were lit on Tuesday near Bream Bay school, a shopping centre and the racecourse. There are no reports of property damage.
Fire officers are working with police to try and find who is responsible.