The Canterbury Regional Council says a terrible stench lingering around Timaru for several days is likely to be wafting from a food processing plant.
The council has received about 90 complaints from residents who have described the odour as fishy, meaty or even like sewerage.
Council enforcement officer Lance Corcoran says it is not uncommon to get complaints about odours during the summer months, as the port and several food processing plants are nearby.
However, he says this stench is particularly bad and has spread further afield.
Council staff have been trying to track the source of the odour and are speaking with the owners of processing plants.