Mitchell Dale Stehling told family members at approximately 4 p.m. Sunday that he was going to hike to the Spruce Tree House near the park's headquarters. When Stehling did not return Sunday, family alerted park officials.
Park crew members searched Spruce Canyon, Spruce Tree House, Petroglyph Trail and other trails on Chapin Mesa.
Temperatures in the park Wednesday were in the 80s. The terrain consists of steep canyons and mesa tops at elevations between 6,500 feet and 8,000 feet.
"We have between 30 and 40 people out there right now," Mesa Verde public information officer Betty Lieurance said Wednesday morning. "We have two dog teams and a couple of people on horseback and helicopter. Searchers today are heading up from the canyon bottom up to the cliff top. They'll be going through some incredibly dense vegetation."
Lieurance said the search efforts will continue indefinitely.
"We don't have plans to stop the search at this time," Lieurance said.
Lieurance said Mesa Verde hikers usually don't go missing this length of time.
"It's usually because they took a wrong turn and we find them or they redirect themselves within two to five hours," Lieurance said.
The park is home to mountain lions and black bear. Lieurance said the last reported mountain lion attack of a hiker was in 1997.
"We're still hopeful that we'll find him," Lieurance said. "Obviously, as the search goes on, that hope goes down a little bit."
The trails in Mesa Verde are very strenuous with steep inclines and drops. Stehling was last seen hiking to the Spruce Tree House to view cliff dwellings.
"There are places where you can fall," Lieurance said. "You can see the Spruce Tree House from the headquarters area. We're thinking he got off on the Petroglyph Trail rather than the Spruce Tree House. All of the hikes here are somewhat strenuous because you're going down and then you have to go up at a higher elevation."
The park is spread over 52,000 acres. Stehling was last seen wearing a brown shirt and hat, khaki shorts and hiking boots. He was not carrying any water or other gear.