Michigan officials say no genetic material from Asian carp turned up in 200 water samples taken from the Kalamazoo River in July.
The samples were taken by the U.S. Fish and Wildlife Service, which is monitoring Great Lakes tributaries for signs of the invasive fish.
DNA from bighead and silver carp has been detected in Chicago-area waterways, raising concerns that they may be near Lake Michigan. Both were imported from Asia. Officials are trying to prevent them from reaching the Great Lakes, where they could out-compete native fish for food.
Other Great Lakes tributary rivers also have been sampled for Asian carp DNA. Results will be released later this year.
The Michigan Department of Natural Resources is asking boaters and anglers to report fish they think may be Asian carp.