TULSA, Okla. (AP) – The Cherokee Nation is appealing a federal judge’s ruling that blocked the tribe from joining Oklahoma’s water pollution lawsuit against 11 Arkansas poultry companies.

Cherokee Nation Attorney General Diane Hammons filed a notice of appeal Thursday that the tribe would take its case to the 10th U.S. Circuit Court of Appeals in Denver.

On Tuesday, U.S. District Judge Gregory K. Frizzell denied the tribe’s request to be added as a plaintiff in the case, paving the way for the trial to begin Thursday. Frizzell said the nation could still bring a separate lawsuit against the companies.

“We have to appeal to protect our interest in the Illinois River,” Hammons said Friday. “If we don’t remain a part of the case, both sides can ignore our interests in this precious resource.”

Oklahoma Attorney General Drew Edmondson sued the companies in 2005, claiming that the estimated 345,000 tons of chicken waste produced in the Illinois River watershed each year has wreaked environmental havoc on the land.

The state claims that runoff carries bacteria into lakes and streams and threatens the health of tens of thousands of people who boat and camp in the river valley every year.

The 1 million-acre watershed spans parts of Oklahoma and Arkansas and is dotted with 1,800 poultry houses, most in Arkansas. The industry employs more than 55,000 people in the two states, and the area produces a large number of the nation’s broilers.

Gary Mickelson, a spokesman for Tyson Foods Inc., one of the defendants, said Friday the companies were looking “forward to presenting evidence that proves poultry producers are abiding by state regulations in their use of poultry litter as a fertilizer.”

In another pretrial matter, the number of companies being sued by the state dropped from 12 to 11. The state initially named Cal-Maine Farms, Inc. as one of the defendants, but that company doesn’t do business in the watershed, so Frizzell, the trial judge, dismissed the company from the lawsuit.

Cal-Maine Foods, Inc. remains a defendant. The other companies named include Tyson Poultry Inc., Tyson Chicken Inc., Cobb-Vantress Inc., Cargill Inc., Cargill Turkey Production L.L.C., George’s Inc., George’s Farms Inc., Peterson Farms Inc. and Simmons Foods Inc.