Kazakhstan's Emergency Situations Ministry said the maximum permissible concentration of cyanide in the river Sekisovka, Glubokovsky district, East Kazakhstan region, has been exceeded by 516 times, Itar-Tass reported.
The tests were taken on October 31, 2011. The source of the leak has not been found yet. Local residents said the waste had come from the local gold-mining company.
Samples of dead fish found in Lake Sekisovskoye have been sent for tests.
The Ministry has launched detoxication measures.