People are still being advised not to swim in, or drink out of Lake Tarawera.

Water testing is underway after concerned Te Rata Bay residents reported the water was an unusual milky colour.

A Bay of Plenty Regional Council spokeswoman says they'll have the test results back by the end of the week.

She says in the meantime people should avoid contact with the water.

The milky colour could be caused by geothermal activity or algal blooms.