A large quantity of used oil or diesel has been discharged into the public sewer system in the vicinity of Wied il-Lunzjata, Gozo, the Water Services Corporation said last night.
In a statement, the WSC said that during last Friday's power failure, the pumping station in Wied il-Lunzjata, which leads to Xlendi, stopped working and sewage with waste oil floating on top overflowed into the valley.
Workers from the Wastewater Section of the WSC as well as officers from the Civil Protection Department are cleaning up the area, though access is difficult.
It is estimated that at least 400 litres of the oil or diesel mixture overflowed and most of it has to be removed manually.
The corporation said the oil was dumped illegally. Police are investigating.