A crippling water shortage in the Far North has created a black market, with thousands of litres of water taken from council-owned fire hydrants.
The Far North District Council banned the use of sprinklers, unattended garden hoses and irrigation devices earlier this month.
Since then, very little rain has fallen, and even tougher water restrictions were likely as another dry week was predicted.
The Council said about 90,000 litres of water had apparently been stolen from Okaihau and Rawene, as water levels were lower than expected.
Far North mayor John Carter said he suspected the thefts were for personal - rather than financial - gain.
"We did have a reasonable rain, and tanks got filled last Saturday, and there has been no more unknown water usage since then, so we suspect it's more to do with people topping up their own tanks, but we are worried about it."
Police in the area were also looking into reports of water being stolen from a commercial property in Kerikeri.
Mr Carter said people should only accept water from members of a list of legitimate sources.
Council spokesperson Jacqui Robson said residents buying bulk water to replenish their tanks should check their supplier was registered with the Ministry of Health.
The council was also worried water taken from streams was being sold as treated water.