GEORGE TOWN - A strong stench permeated the air as hundreds of dead fish littered the mouth of Sungai Bayan Lepas.
To make matters worse, flies had a feast after the water level subsided in Permatang Damar Laut.
The sudden mass fish death has raised environmental concerns among residents and fishermen living nearby.
Fisherman Saidin Ismail, 69, who has been fishing in the area for decades, said the sight of dead fish shocked him.
"It's happened before but never this severe. Last year, there were dead fishes floating in the river but it was never this much. This could be due to pollution," he said.
State Local Government Committee chairman Chow Kon Yeow said water samples had been sent to the laboratory for tests.
He said Drainage and Irrigation Department (DID) and Department of Environment (DOE) officers visited the site to conduct checks.
"They took away water samples. It will take around two weeks for the results to be out.
"According to DOE, the dead fish are mullets which are usually near the river mouth.
The incident could be due to pollution at the river mouth," he said in a statement.