Yellowstone National Park rangers are investigating whether a man found dead along a trail was killed by a grizzly bear.
The man was found Friday morning by two hikers on the Mary Mountain Trail in the central section of the park. Authorities announced the death Saturday but did not name the man.
Officials said the hiker was in his 60s and a native of Michigan, but withheld further identification pending family notification.
A release from the park said there were "signs of grizzly bear activity at the scene" but that there was no immediate determination of how the man died. Authorities say he likely died Wednesday or Thursday.
The 21-mile-long trail north of the Old Faithful geyser is closed from March to June because park managers list it as "high-density grizzly bear habitat." A park release said that an aerial search of the area Saturday morning failed to turn up any current bear activity.
Hikers on the trails still open were advised to stay on marked trails, hike in groups of three or more people and to make noise and carry bear pepper spray.
Last month, a 57-year-old California man was attacked and killed by a female bear on the popular Wapiti Lake Trail, several miles away from where the Michigan man was discovered.
The female bear that killed the California man was not killed because officials said the sow was only defending its cubs and had not threatened humans before.