Thirteen bison were killed near Yellowstone National Park after being struck by a semi-truck, police said Saturday.
The accident happened last Wednesday at mile marker four on U.S. Highway 191, between West Yellowstone, Montana, and Highway 287. The bison were initially thought to have been hit by both the semi and two passenger vehicles, but police later said the passenger vehicles were involved in a secondary collision, the West Yellowstone Police Department said.
Some of the bison had to be euthanized due to their injuries.
"We deal with wildlife being struck and killed on the roadways in our area on a regular basis due to the abundance of wildlife in our area and our close proximity to Yellowstone National Park," police said. "We are always saddened by any of these incidents, particularly when so many animals are lost."
The bison in the area often move toward paved roads during the winter time as the conditions make it easier for them to travel. Police urged travelers to slow down in accordance with road and weather conditions.
"Although speed may not necessarily have been a factor in this accident, road conditions at the time would dictate traveling below the posted speed limit," police said.
The Montana Highway Patrol is investigating the incident.
