INDIANAPOLIS (AP) — Avian influenza has been detected in a northern Indiana duck farm, state officials say, marking the disease’s spread to a third poultry species.

The Indiana State Board of Animal Health said Thursday night that laboratory testing of a commercial duck flock in Elkhart County has come back as presumptively positive for the virus.

It says the samples are being verified at the U.S. Department of Agriculture’s National Veterinary Services Laboratory in Iowa.

The agency says the duck flock has an estimated 4,000 birds, the agency said.

Bird flu was detected earlier this year at six turkey farms in southern Indiana’s Dubois and Greene counties.