A Minnesota woman was severely injured by a bison in Theodore Roosevelt National Park in Medora, North Dakota, according to the National Park Service.

It's the second instance of a bison injuring a person in the past week. A bison gored a 47-year-old Arizona woman Monday morning in Yellowstone National Park in Wyoming.

In the wake of the two incidents involving national park guests within days of each other, the National Park Service has issued a warning that bison can be easily agitated during mating season.

"Bulls can be aggressive during the rutting season, mid-July through August. Use extra caution and give them additional space during this time," the park service said.

NPS said the exact details of what happened to the Minnesota woman are so far unknown, but the July 15 incident at Painted Canyon is under investigation.

"Park staff send their sincere well wishes to her and her family as she continues to receive care and recover," NPS said in a news release.

Park rangers and the Billings County Sheriff and Emergency Medical Services responded to the Painted Canyon Trailhead around 11 a.m. and treated the woman until she was taken by ambulance to a local hospital. She was then taken to a hospital in Fargo for "significant injuries to her abdomen and foot," according to the park service.

The Arizona woman also sustained significant injuries -- in her case, to the abdomen and chest -- after being gored. She was walking with another person in front of a lodge on the north shore of Lake Yellowstone when they saw two bison, Yellow Stone National Park said in a news release.

They turned to walk away from the bison, but one of the animals charged, goring the woman, the release reads.

"Park staff would like to remind visitors that bison are large, powerful, and wild. They can turn quickly and can easily outrun humans," the park service said.

NPS said national park regulations require that visitors stay at least 25 yards away -- the length of two full-sized busses -- from large animals such as bison, elk and deer.

"Approaching bison threatens them, and they may respond by bluff charging, head bobbing, pawing, bellowing, or snorting," according to the park service. "These are warning signs that you are too close and that a charge is imminent."

Bison have injured more people in Yellowstone than any other animal, the park service said.