Waupaca County, Wisconsin, officials hope that a cash reward will lead them to those responsible for allegedly sexually assaulting a pregnant mare while she grazed in her pasture in New London.

A Waupaca County Sheriff’s Department spokeswoman said department personnel responded to a call from an owner reporting that his 15-year-old pregnant mare was found injured and bleeding on Nov. 29. She said the animal was allegedly sexually assaulted, but declined to disclose any further information.

“It’s an open investigation,” she said.

While the probe continues, the Humane Society of the United States is offering a $5,000 cash reward for information leading to the arrest and conviction of those responsible