Bay of Plenty Regional Council staff are in the process of hunting down the cause of a spill which has turned the water milky in a Bay of Plenty harbour.

A post on the council Facebook page on Monday shows milky-looking water near a shoreline, and another of a gloved hand and a sample bottle – but no details about which harbour; Tauranga, Whakatane, or Ohope.

This is deliberate, says a spokesperson.

The council was called about cloudy material entering the harbour through a storm water drain. Photo: Supplied.

'We are making the most of the opportunity to get enough detail to investigate.”

Council staff were told about cloudy material entering the harbour through a stormwater drain earlier this week. Samples have been taken for testing.

'Remember storm water drains are just for rain and do not filter the paint, cigarette butts or other items people discard out their windows or down the drain. It won't all come out in the wash and it all ends up in the harbour.”

Samples have been taken. Photo: Supplied.