Firefighters and a HazMat crew worked to mop up the diesel, which had been discharged into the harbour.

Kiama’s Fire and Rescue NSW crew and Shellharbour’s HazMat team used booms to sweep excess oil out of the water via the boat ramp.

It is understood the spill came from one of the vessels on the harbour, but the emergency crews were unable to identify the source of the spill.

The spillage has been contained, but the spill remains visible around the edges of the harbour.

There is a strong oil smell at the area closest to the Scouts building.

Council rangers were on site, and have made efforts to identify the source of the spill.