Reports of general household and green waste being disposed on public land at night and during weekends had risen over the past few months, a trend that has council staff concerned.
Waitaki District Council environmental services manager Jason Evered said most of the dumping was in and around Oamaru, including Kakanui, and on dead-end roads that ended at the Oamaru foreshore.
Dumping had also taken place on private land outside Oamaru.
Food packaging, used nappies, glass bottles and green waste such as hedge and tree clippings and offal were frequently dumped.
Mattresses, sheets and clothing have also been dumped.
Mr Evered attributed the activity to a small section of the community who "decide not to deal properly with the waste they create".
The council was investigating recent cases of illegal dumping, he confirmed.
"No individuals have yet to be identified. However, investigations are ongoing for at least two incidents.
"Information has been supplied by the community about possible individuals concerned in at least one of these dumpings and details of a possible vehicle involved."
He said the council was asking for help from the public through social media, letterbox drops in specific areas, its website and local newspapers to identify those responsible.
"Appeals are being made to the local community on two fronts, for people to do the right thing when disposing of rubbish and to report suspected illegal dumpers to the council.
"On receipt of complaints of actual dumping, contractors and or council officials are sifting through dumped rubbish looking for evidence of who dumped it."
Under the Litter Act 1979, offenders can be prosecuted and fined a maximum of $5000 for dumping rubbish illegally and also be ordered to pay for the disposal of the rubbish.
If the rubbish had the potential to cause injury, such as forms of glass, the maximum fine was $7500 and up to one month imprisonment.
The council can issue an infringement notice of $400 and seek the recovery of disposal costs.
Submissions were also being sought on the council's draft Waste Management and Minimisation Plan 2018-24.
