Aucklanders are being warned of the risks of swimming at several popular beaches after a landslide reportedly caused wastewater to run into the sea.

Water quality monitor Swimsafe raised a “black flag” at St Heliers and Kohimarama - which comes as the city faces a week of warm weather.

A landslide on Parkside St, off St Heliers Bay Rd, took out a wastewater manhole cover, causing sewage to run into the stormwater network which flows to sea, Deputy Mayor Desley Simpson said.

Simpson said council workers were investigating a solution to restore “service” and keen swimmers would be kept updated.

Swimsafe has deemed swimming at either beach presented a “very high risk” and said work was underway to solve the sewage overflow.

Water quality monitor Swimsafe raised a “black flag” at St Heliers and Kohimarama - which comes as the city faces a week of warm weather. Photo / Swimsafe

Judges Bay in Parnell also has a black flag warning along with six other beaches about the city.

Beach Haven, Soldiers Bay, Waiakae Beach and Castor Bay on the North Shore have black flags raised, as well as French Bay and Māngere Bridge.