The Wisconsin Department of Natural Resources (DNR) is investigating cases where pet dogs and wildlife were fatally poisoned in three Wisconsin counties, according to Fox 6.

Since December, at least four domesticated dogs have died from eating poisoned meat in Bayfield, Marinette and Florence counties, according to the Wisconsin Department of Natural Resources. Investigators also found dead coyotes, raccoons, weasels and a wolf in the impacted areas.

The animal deaths occurred on public lands managed by the U.S. Forest Service and Goodman Timber Company.

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The DNR says there's a possibility this could be happening in other counties.

The poison was found on the ground of those public lands and each dog died less than 30 minutes after ingesting the poisoned meat, according to the DNR.

Clark Cate, a resident in northeast Wisconsin, was out walking his three-year-old German shorthaired pointer named Ava when he saw his dog eating something. The dog ran into the woods and at first he thought she’d gotten into deer droppings.

"About 10 minutes later she staggered out into the road and started convulsing and hyper-salivating and died in my arms about 20 minutes later," Cate told Wisconsin Public Radio.

He took a sample of the poison to a veterinarian, who suspected Ava may have been poisoned by fly bait.

"It [the poison] was mixed in with hamburger and thrown in the woods," Cate told WPR. "Everybody’s surmising that it was put out to kill wolves."

DNR says they are investigating before they can determine a reason for these deceased animals, although they suspect it may be pesticide carbofuran, a chemical used to control insects in a wide variety of field crops, including potatoes, corn and soybeans.

Investigators say each dog died within 30 minutes after eating the substance and lab tests are underway to determine a cause of death.

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"In all four cases where the dogs died, the poisoned meat was found in a road ditch," Capt. Dave Zebro, northern region conservation warden for the DNR told WPR. The DNR put out a statment telling dog owners to keep their pets on a leash when outside and keep them away from roadside ditches.

The DNR sent samples of the tainted meat to the Wisconsin State Crime Lab for testing. In addition to the DNR, the U.S. Forest Service and U.S. Fish and Wildlife Service are also investigating these deaths.

If you have any information or a tip, please contact the Wisconsin DNR hotline at 1-800-847-9367.