Three Utah taxidermists have pleaded not guilty to federal charges they illegally killed and sold wild game and birds.

David Butts, Troy W. Garner and Michael Tracy Jacobsen were arraigned Monday before U.S. Magistrate Ronald Boyce.Butts is scheduled to stand trial May 13, and Jacobsen and Garner are to begin trial on May 20 together. The cases will be heard by U.S. District Judge David Sam.

Federal prosecutors announced on Friday that the men's arrests came after a four-year, five-state undercover operation dubbed Operation Wasatch. They said as many as 100 more arrests may be made as the probe continued in Utah, Idaho, Alaska, California and Nebraska.

Butts, 29, of Ogden, was named in a nine-count indictment with selling migratory birds, a black bear, a pronghorn antelope and a sandhill crane between August 1989 and November 1990.

Jacobsen and Garner were named in a separate indictment. Jacobsen, 23, of Springville, was charged with three counts of selling wild ducks. Garner, 20, of Highland, faces one count each of bartering migratory birds and being an accomplice in the sale and purchase of wild ducks.

Boyce permitted Garner, who had been detained since his arrest Friday, to post a $10,000 signature bond. He had been detained at the request of prosecutors who said his release could endanger undercover officers.

Butts and Jacobsen each posted $10,000 signature bonds Friday.