Tauranga City Council staff are trying to find out why bacterial levels are failing to fall after two separate sewer leaks about the city.

A fat blockage caused a small sewer overflow into the Judea open drain alongside the Judea sports ground on December 17. The blockage was cleared, the affected area disinfected and health warning signs put up alongside the drain.

Results from samples taken on January 5 show there are still elevated bacterial counts and health warnings remain in place.

'It is unlikely the elevated levels are the result of the original overflow and we will conduct further investigation next week,” says council group communication advisor Alison Clifford.

The Kaitemako Stream also continues to show high bacterial levels after a pipeline blockage on October 28 caused a sewer overflow into the stream.

The high bacteria counts are both above and below the original overflow site and are thought to have another cause.

'We will be working with Public Health to investigate further,” says Alison.