Collecting shellfish and swimming in part of Nelson has been banned after a sewage spill caused by flooding on Friday.
Nelson District Council is warning people not to come into contact with water until further notice in Nelson Haven and at Tahunanui Beach.
District health protection officers, the Ministry of Fisheries, the Department of Conservation, pollution control officials and iwi have been notified.
Homes and garages in Nelson were flooded on Friday and streets were closed following heavy rain in the city.
Up to 75mm of rain fell, most of it between 7am - 9am on Friday.
Nelson City Council received about 80 calls.
The Fire Service says much of the flooding was caused by blocked drains.