Illegally introduced non-native snakeheads are likely to spread through from Maryland and Virginia to Pennsylvania and West Virginia, says The Washington Times.
Three Northern snakeheads have already been caught this month in the Potomac River, prompting fears that the fish might be breeding again.
Fisheries Biologist William Loftus, of the Geological Survey's Florida Everglades National Park, told The Washington Times: "It's bad news. If there is a large enough population of breeding adults in the Potomac, it's likely the animals will be moving into other states."
Prior to the three snakeheads caught in the past few weeks, no other specimens have been caught following the lake full of adults and youngsters found in Maryland last year.