Whangarei District Council is investigating a foaming white spill in a local stream.
A member of the public reported the spill behind Whangarei RSA to the Northland Regional Council on Monday.
Colin Dall, monitoring programme manager for Northland Regional Council, said it appeared to be a detergent-like foam, rather than something naturally occurring.
It appeared to have entered the Waiarohia Stream through a stormwater pipe 30 to 40m upstream of the Lovers Lane bridge, behind the Whangarei RSA, Mr Dall said.
"Despite a full investigation of the stormwater system that receives runoff in the catchment surrounding Cafler Park, including inspections of schools, businesses and the fire station within the stormwater catchment, the source of the foam was not found."