Mass die-off of fish at Lake Cajititlan in western Mexico shrouded in mystery

AUTHORITIES investigating why tens of thousands of fish have died out en masse at a lake in western Mexico say it was not due to natural causes.

Local fishermen collect dead "popocha" fish at the lagoon of Cajititlan in Tlajomulco de Zuniga, Jalisco State, Mexico, on September 1, 2014. At least 48 tonnes of fish have turned up dead in a lagoon in western Mexico and authorities are investigating whether a wastewater treatment plant is to blame. Officials in the state of Jalisco said late Sunday it was the fourth case of mass deaths at the Cajititlan lagoon this year in the town of Tlajomulco, south of Guadalajara. AFP PHOTO/Hector Guerrero

MEXICAN authorities say a mass die-off of fish at a lake in western Mexico was not due to natural causes.

Over 33 metric tons of rotting dead fish have been removed from Lake Cajititlan in Jalisco state.

The cause of the die-off has not been determined but the state environment department said late Sunday it was not due to natural causes.

Workers using shovels, a bulldozer, boats and wheel barrels removed the dead fish, which are being sent for testing.

Clean-up ... A fisherman collects dead "popocha" fish at the lagoon of Cajititlan. Picture: Hector Guerrero/AFP

The small, finger-sized fish are apparently a type of chub.

It was the fourth time this year there has been a die-off at the shallow lake, which sits between Guadalajara and Lake Chapala.

Some had speculated abrupt changes in temperature or oxygen levels may have been responsible for earlier incidents.

Unnatural disaster ... Mexican authorities say the mass die-off was not due to natural causes. Picture: Hector Guerrero/AFP

Originally published as Mass die-off of fish at Lake Cajititlan in western Mexico shrouded in mystery