Up to 41,000 litres of sewage has ended up in Whangarei Harbour after a "technical glitch" meant a leak went unnoticed for three days.
It was only after Onerahi residents kicked up a stink over the smell that Whangarei District Council contractors discovered the fault.
A sewage pumpfailed last Friday, but the problem went unnoticed until Monday morning.
Now the council is warning people to keep out of the water for a week and not collect shellfish for 28 days.
The warning applies to the area from Kissing Pt to the Onerahi Yacht Club. Anglers have also been told not to eat fish caught since Friday in the upper harbour.
Whangarei District Council waste and drainage manager Gary Oldcorn said an alarm system at the pumping station near Pah and Beach Rds failed to alert council contractors on Friday.
The spill was fixed by 10am on Monday, but by then between 11cu m and 41cu m - up to 41,000 litres - of sewage had spilled into the harbour.
Mr Oldcorn said it was a concern a "technical glitch" meant contractors had not been alerted to the leak. An investigation had been launched.
Northland's medical officer of health, Jonathan Jarman, said the fine weather meant people were more likely to be on the water, making the spill a medium health risk.
The contaminated water could cause gastrointestinal illness or skin and respiratory infections.
