BILLINGS, Mont. (AP) — State livestock officials are among those investigating after up to two dozen horses were shot dead and dumped in a hay field about a mile west of Lodge Grass on the Crow Indian Reservation.

The Billings Gazette reports (http://bit.ly/1CzYya8 ) residents looking for their missing horses found the dead animals last week.

Law enforcement officers from several agencies along with officials from the state Livestock Department investigated the deaths on Feb. 11. Some of the horses' heads were cut off.

Horses are allowed to roam freely on the reservation because it is open range.

Livestock Department executive officer Christian McKay says killing roaming livestock in open range country is illegal. It was not immediately clear on Friday what legal action might be taken.