Pesticides were found in water samples taken from rivers in western P.E.I. where thousands of fish were found killed. CBC

Environment Canada has found traces of pesticides in water samples from three rivers in western P.E.I. where thousands of fish were found dead last week.

The fill kills were discovered in the Big Pierre Jacques River and in the Mill and Trout Rivers.

"All those samples were collected and submitted to the Environment Canada laboratory for analysis," said Robert Robichaud, Environment Canada environmental enforcement manager. "Some of those samples have come back. I can confirm that the water samples, or some of the water samples that were analyzed to date did show pesticides in some of the areas that were affected."

Robichaud said Environment Canada has launched an investigation into the incident.

He said the investigation could lead to charges. That would mean a fine of up to $300,000 or six months in prison.

Robichaud said officers took samples from water sediments and fish and they are still waiting for word on the fish tissue samples.