Authorities are investigating the deaths of thousands of fish due to a molasses spill in the western state of Jalisco, a spokesman for Mexico's Profepa environmental protection agency told Efe.

An investigation was opened on Monday after officials received complaints from the Los Pinos fishing cooperative in the city of Acatlan de Juarez, where the Hurtado dam is located, and the government of the city of Tlajomulco.

The fish kill was apparently caused by an "environmental accident," the Profepa spokesman said.

Molasses "is not a toxic substance," but it produced a chemical reaction that eliminated the oxygen from the water and killed the fish, the Profepa spokesman said.

A local business dumped the molasses in a ravine and it was washed into the sea by the rain.

The fish kill affected about 80 families that earn a living off fishing. EFE