Authorities say lab tests have not shed any light on what led to the deaths of two dozen cows in the Heber and Overgaard area.
The Navajo County Sheriff's Office said Friday that samples taken after the cows were found last week have tested negative.
Further testing will be done by the state veterinarian.
A Heber rancher reported two dead cows earlier this month. That was followed two days later with 14 cattle being found dead in the same area.
So far, it appears the cattle all suffered a "natural occurring ecological poisoning" caused by forest conditions.
The investigation remains ongoing with assistance from state Game and Fish Department and the U.S. Forest Service.
