Two of Wanganui's largest wet industries say they are not responsible for dumping solid waste into Wanganui's wastewater treatment plant, causing it to malfunction.
A large amount of protein material recently reached the plant through the Beach Rd pumping station, and the Wanganui District Council is trying to trace who was responsible.
The plant's aerators have had to be shut down and the unpleasant smell has wafted throughout the city.
Open Country Dairy milk processing plant and Affco Imlay meat processing plant both say they did not illegally dump the solid waste.
Scott Houston, the manager of Open Country Dairy's Wanganui operations, said his company was not responsible and council officers had not approached management to talk about the dumping.