PORTLAND, Ore. (AP) — Investigators with the Oregon Department of Fish and Wildlife are offering a $1,000 reward for tips that lead to an arrest in the shooting of mule deer with blow gun darts in eastern Oregon.

Oregon State Police troopers found the carcass of a fawn in the city of Burns in November, The Oregonian/OregonLive reported. The animal had a blow gun dart lodged in its neck.

Three more mule deer were found in following months, but biologists were able to remove the darts and release the animals.

On Feb. 13, troopers got a call about an injured doe in the city. The animal had a dart stuck in her side, officials said, and had to be euthanized.

It is illegal to hunt deer with blow guns in Oregon. While the darts are effective at killing smaller animals like rabbits and squirrels, blow guns can cause slow and painful deaths in larger animals, according to Rod Klus, a state biologist.

Investigators ask anyone with information about the poaching incidents to contact Oregon State Police by calling the agency’s tip line at 800-452-7888 or by email at TIP@osp.oregon.gov