A 59-year-old American man has died after being mauled by a grizzly bear in Yellowstone National Park, officials said.

Officials identified the man as John Wallace of Michigan and said he was camping alone in the vast park in Wyoming. His body was found Friday.

"Results from an autopsy conducted Sunday afternoon concluded that Wallace died as a result of traumatic injuries from a bear attack," the National Park Service said in a statement.

"Rangers discovered signs of grizzly bear activity at the scene Friday afternoon, including bear tracks and scat."

Wallace was the second person to die from a bear attack in the past two months in the famed US park, after a 57-year-old man killed in July. Still, officials say deaths from bear attacks remain very rare in Yellowstone and that the latest before this year were in 1986.

"Visitors are advised to stay on designated trails, hike in groups of three or more people, be alert for bears, make noise, carry bear spray, and not to run upon encountering a bear," the park service said.