Canterbury District Health Board is warning people to not eat shellfish from the coastline between Motunau Beach and Akaroa Harbour.

This comes after shellfish samples reveal Diarrhetic Shellfish Poisoning toxins which are above the safe limit.

It can cause diarrhoea, vomiting, nausea and abdominal cramps to appear within half an hour - and those symptoms can last up to a day.

Monitoring of toxin levels is continuing.