A sewer leak at a popular Christchurch swimming spot has been traced to bottles being flushed down toilets, blocking the septic system

The City Council says the blockage at Corsair Bay caused wastewater to overflow into a small holding tank, while a separate fault in an outdoor shower also sent water down a pathway.

Contractors are now working to fix the system so facilities can reopen as soon as possible.

Environment Canterbury and the council are carrying out water quality testing over the coming days, but the impact of runoff into the bay remains unclear.