Authorities say no foul play is suspected in the deaths of two dozen cows in the Heber and Overgaard areas.
Navajo County sheriff's officials said Thursday that ranchers in the last few days have reported finding cattle deceased.
They say a Heber rancher reported two dead cows on Sunday. That was followed two days later with 14 cattle being found dead in the same area. Other reports have come in since.
Sheriff's deputies say several samples have been collected from the cattle for testing by a state laboratory.
So far, it appears the cattle all suffered a "natural occurring ecological poisoning" caused by forest conditions.
The results of toxicology tests are not yet completed.
The investigation remains ongoing with assistance from state Game and Fish and the U.S. Forest Service.