MINNEAPOLIS (AP) — Tests on over 750 ducks shot by Minnesota hunters this fall have turned up no signs of the kind of bird flu that devastated the Midwest poultry industry earlier this year.

Researchers are testing wild waterfowl to see if ducks flying south for the winter are carrying highly pathogenic forms of avian influenza such, which could provide an early warning if the disease returns. Wild waterfowl don't normally get sick from these viruses, but they're deadly to domestic poultry. Bird flu cost producers more than 48 million chickens and turkeys earlier this year, mostly in Minnesota and Iowa.

Lou Cornicelli of the Department of Natural Resources tells The Associated Press that none of the 753 Minnesota duck samples tested so far came back positive for highly pathogenic flu strains.