Natural causes or pollution are being considered as an environmental probe ramps up over a Lake Macquarie fish kill.
More than a hundred fish of various species and sizes, including stingrays, were found washed up on the shore at Manning Park over the weekend.
A boat was sent out by the Environment Protection Authority to look for signs of pollution in the waters with officers deploying drones to establish the extent of the fish kill.
Samples of fish and water have been taken and the test results will help determine if the event has a natural cause.
The EPA says greying around the fishes gills points to oxygen depletion.
While their investigations hinge on lab results, officers will begin the process of clearing the waterways today.