FAIRPLAY, Colo. -- Officials plan to fly over the properties in Park County where 32 bison were killed to determine whether the death toll is greater.

Park County Undersheriff Monte Gore said it's possible they will find more dead bison but he didn't say why. He said the flyover will depend on the weather Friday.

The animals belonged to ranchers Monte and Tracy Downare but were found on or near the neighboring Hawn Ranch, other property and federal land belonging to the Bureau of Land Management and U.S. Forest Service. The Colorado Bureau of Investigation is also looking into the slayings south of Hartsel. The CBI is concentrating on forensic evidence from the bison carcasses.

About a dozen hunters told investigators they had permission to shoot the bison last week, but it's not clear who gave them the OK. They had been staying in a barn, outbuildings, and tent on the Hawn property, and shot the bison over several days, the undersheriff told the Rocky Mountain News.

Park County Sheriff Fred Wegener said he believes the shooting stems from a civil dispute. The shootings last week occurred just days after Jeff Hawn, a Texas businessman, filed a lawsuit claiming Downare's bison repeatedly broke through fences and damaged his property.

The ranchers have declined comment.

Wegener said he "probably" will recommend charges in the case and that the Park County district attorney's office. Charges of aggravated cruelty to animals are being considered because of the way the carcasses were abandoned, Wegener said.

Trespassing and evidence tampering charges could also be filed.