Don't release your pet goldfish into the lake! That's the plea made by the authorities of the city of Burnsville, Minnesota.

Several goldfish that were dumped into a local lake have grown enormously, reaching the size of an American football.

Now, these oversized fish threaten the local ecosystem and wreak havoc on native species.

"Please don't release your pet goldfish into ponds and lakes! They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants. Groups of these large goldfish were recently found in Keller Lake," Burnsville authorities wrote on Twitter, attaching photos of the fish.

This is not the first environmental alarm had been raised over goldfish in Minnesota.

Last year, in neighboring Carver County, the Water Management Organization removed an estimated 50,000 goldfish from an inlet connected to Big Woods Lake, which is part of the Grace Chain of Lakes in Chaska.

The organization said the most like scenario is that someone released goldfish into the lake and the hardy fish began to multiply.

Big Woods Lake has relatively poor water quality and few other predatory fish species, conditions that have allowed the goldfish to multiply, Minnesota Public Radio News reported.

Fisheries biologist professor at the University of Minnesota, Peter Sorensen, said goldfish haven’t gotten as much attention as invasive carp, but they are causing significant problems in parts of Europe, Canada and Australia as well as the United States.

"It just hasn’t reached a high level of awareness," he said. "They don’t jump and knock people out of boats and break bones. But it’s a global issue."