Searchers so far have been unable to find any sign of a 25-year-old Oklahoma man thought to be missing somewhere in the northern range of Yellowstone National Park, officials said Friday.

A search for Peter Louis Kastner, of Oklahoma City, has been under way since a car he had rented in Oklahoma was found this past Monday morning at the Hellroaring Trailhead several miles west of Tower Junction.

The man had not applied for a permit to camp out overnight in the backcountry at one of the many campsites along the trail system in the area which leads to and parallels the Yellowstone River.

A subsequent investigation revealed the red Cadillac STS sedan with Oklahoma plates had been rented a month earlier and was two weeks overdue. Family members who were then contacted reported they had not been in touch with Mr. Kastner in recent weeks, and reported him missing.

The missing man is described as 6-foot-1-inch tall, weighing 185 pounds, with brown hair and hazel eyes. Based upon information from his family, he was honorably discharged from the Marine Corps after serving for four years. During his service, he was injured twice by Improvised Explosive Devices while serving in Iraq. He had moved to Oklahoma City from the Minneapolis - St. Paul, Minnesota, area to attend college. His family is concerned about his mental state, and said he was suffering from Post Traumatic Stress Syndrome
related to his injuries.

A series of searches by ground teams and dog teams have failed to turn up any clues to his whereabouts, as has a call for the public to report any sightings of Mr. Kastner in the area prior to Monday morning, park officials said Friday afternoon.

Investigators still believe he is in the park. Search efforts are slated to ramp up again this weekend, as ground searchers and dog teams will again focus on the backcountry northwest of Tower Junction. Cloudy, rainy weather, a low ceiling, and a lack of a focused search area has led searchers to focus efforts on the ground rather than utilizing helicopters or fixed wing aircraft.

There is a chance the man is no longer in Yellowstone. Investigators in the area are asking anyone who may have seen or been in contact with Mr. Kastner in recent weeks to call Yellowstone National Park at 307-344-7381.