My wife and I are into TV crime dramas like Crime Scene Investigation (CSI) where the bad guy gets nailed if he so much as sneezes on a dinner napkin.

Well, Asian carp are pretty slimy critters, so if they’re swimming in your waters, they’re going to leave some evidence. A recent water sample from Lake Michigan’s Sturgeon Bay in Wisconsin has tested positive for Asian Carp DNA, the Associated Press reports. This is second time Asian Carp DNA has been found in the lake.

In May, 50 Sturgeon Bay samples were collected and analyzed by researchers with the University of Notre Dame, Central Michigan University and The Nature Conservancy as part of a broader Great Lakes fish survey.

Although even one hit is worrisome, scientists stressed it’s unknown whether the genetic material came from a live fish, as droppings from birds that have consumed carp can transfer DNA.

“One sample is a smoke detector,” said Chris Jerde, a Notre Dame biologist, told AP. “A couple of more samples is a fire.”

Nevertheless, if non-native Asian carp have reached Lake Michigan, the threat cannot be overstated. Captive carp were imported decades ago, but after escaping into the wild, they have rapidly expanded throughout the Mississippi River system. The silver and bighead varieties have a track record of environmental calamity, as their voracious appetite for plankton decimates indigenous food chains.

Hopefully, this finding doesn’t escalate from detection to damage control.