Officials with the Army Corps of Engineer say Friday that DNA of the giant carp have been found north of the barrier, which means the carp could reach Lake Michigan if they get through a navigational lock.
Once in Lake Michigan, the fish could move into the Great Lakes, killing the native species.
Asian carp escaped from southern fish farms in the 1990s and have been migrating up the Mississippi and Illinois rivers. They can exceed 4 feet in length and 100 pounds.
(The Associated Press contributed to this report.)