Mexico City, Dhu-AlQa'dah 6, 1435, Sep 1, 2014, SPA -- An investigation was launched into the deaths of hundreds of thousands of fish in a western Mexican lake, environmental authorities said Monday according to dpa. Environmental teams helped by fishermen and other locals recovered more than 33 tons of dead fish at the weekend from Lake Cajititlannear Tlajomulco, south of Guadalajara. The fish were believed to have died from lack of oxygen. Nearby water treatment plants were the focus of the investigation The deaths are "a recurring, ever more intense and frequent phenomenon, caused by bad management of the body of water," said Magdalena Ruiz Mejia, environment minister for the state of Jalisco. The fish kills were the fourth at the site so far this year. Authorities have ruled out natural causes. Samples of the water and the dead fish have been taken to be tested. --SPA 23:28 LOCAL TIME 20:28 GMT www.spa.gov.sa/w