Yellowstone National Park officials are investigating another illegal release of bison, after the Stephens Creek Facility was broken into sometime last night or early this morning.
Park officials said most of the 73 bison that escaped stayed in the immediate area and eventually returned to the pen. Fifty-two bison escaped in a similar incident last month.
Yellowstone National Park Spokeswoman Vicki Regula spoke with Yellowstone Public Radio.
"A criminal investigation has begun. Law enforcement agents are on the scene and are also repairing the fences. And, the park is reviewing security measures at the facility and will make necessary improvements immediately," Regula said.
Bison captured as they leave the park during their winter migrations are slaughtered or held in quarantine for possible relocation at a later date. Some of the animals are intended for transfer to local tribal communities to be processed for meat.
The herd size inside the park currently numbers about 4,800 animals.