There's still no sign of a missing Marine in the rugged Eldorado Canyon State Park where a friend said he fell and suffered a head injury four days ago.The search entered its third day on Friday as 80 searchers were called in to look for Lance Hering, 21, of Boulder.Hering, on leave from duty in Iraq, was free-climbing with a friend on Tuesday when he fell and hit his head. The friend said he stayed with him until he regained consciousness and then left to get help early on Wednesday.That was the last time anyone saw Hering. He was gone when rescuers arrived three hours later at the makeshift camp where the two had spent the night.Since then, searchers have combed the park southwest of Boulder. Search dogs have picked up scents but nothing has led them to Hering.Searchers told 7NEWS that they were frustrated that they haven't been able to find him so far and that there doesn't seem to be an explanation of why he couldn't be located within the first four hours of the search."Something is just not fitting, but they're not sure what," said 7NEWS reporter Dayle Cedars.Criminal investigators were brought in to investigate Thursday. Boulder Sheriff Joe Pelle said Thursday that there ere no indications to believe that what Hering's family and friends have said about his disappearance is not true, but he said something is just not right."Well, my son is a very strong young man, and he's injured. He's been injured before and recovered," said Lloyd Hering, the missing man's father. "He could be just a little confused."Authorities don't believe he hiked out on his own because he would have been spotted by now. Hering had a "substantial" head injury after the fall, rescuers said.One searcher said he found the remains of a fresh kill of a mountain lion. Another searcher said she came face-to-face with a mountain lion Thursday. She said the animal jumped out of a bush, spotted her and ran away."Our worst fear is that he's up here unconscious and hurt really badly or deceased," said Pelle.Anyone with information to offer is asked to contact the sheriffs office immediately at 303-441-4444.Teams plan to continue searching for Hering until Saturday, 7NEWS reported.The sheriff's office said it had sufficient resources available to conduct the search and could not accept casual volunteers who want to help.