DONNA – The Environmental Protection Agency was back out at Donna Lake on Friday, starting the next step on their long clean-up process.

Years ago, they learned what was contaminating fish in the lake. It all starts with the siphon.

Water travels from the Rio Grande and under the Arroyo Colorado which eventually makes its way to Donna Lake.

Mike McAteer, one of the on-scene coordinators for the EPA, says they have been visiting the Rio Grande Valley for over 10 years trying to clean up a mistake.

"So, Donna canal is contaminated with PCBs. Polychlorinated biphenyls. And the fish, unfortunately have got the PCBs in them. And so, what we've been doing for years now is because we can't get people to stop eating the fish, catching the fish and eating the fish, we've been coming out here and we removing the fish as many as we can over a couple of weeks period every year for at least 10 years now," explains McAteer.

PCB is an industrial chemical that could potentially cause cancer and harm pregnant women if they consume it.

McAteer says no one is allowed to go to the lake and "catch or release" any of the fish. He says a new state law now makes it illegal for anyone to possess any fish from the reservoir.

Watch the video above for the full story.