Ranchers in Chino Valley dug trenches Wednesday afternoon to bury dozens of dead cows.

"Whatever killed them killed them fairly quick," neighbor Tom Silva said.

Silva lives in the area and traps small animals for a living. He wanted to see what all the commotion was about.

"There's no struggle," Silva said. "When an animal dies, sometimes it struggles. Its legs move or whatever and it's dying. But these animals just look like they dropped over."

No blood. No gunshots. No one knows exactly killed these beasts.

"Has to be some kind of a poison," Silva said. " I mean, to kill this many and not have any signs of blood or much struggle, it must be a very toxic kind of poison."

The Department of Agriculture was called to the scene to investigate.

A vet from their Arizona Livestock Incident Response Team took samples from the animals.

After some preliminary testing, they believe the animals died from plant toxicity.

"I've lost animals to this particular poison, a plant that grows here," Silva said.

Silva says a plant in the area is responsible for killing several animals. Not just cows.

But he wants to know which one.

"I've lost goats, I've lost turkeys, ducks, if the plant if they eat it, it kills them," Silva said.