A search and rescue effort is underway for a 32-year-old man and three children who did not return from what was supposed to be a day hike in the Weminuche Wilderness on Saturday.

La Plata County Search and Rescue director Butch Knowlton said the group parked at the Cave Basin trailhead at the end of Middle Mountain Road near Vallecito to head toward Dollar Lake in the vast wilderness area.

The family reported they had not returned as of Monday morning.

Knowlton said the missing party includes a 8-year-old twins - a boy and girl - and a 6-year-old boy from the Durango/Bayfield area. Knowlton did not know the relationship of the man to the children.

"They are reported as going up on a day hike," Knowlton said. "That's why there's concern, they haven't been in contact with family members for two days."

Knowlton did not immediately have information on the gear the group was carrying or physical descriptions. He said the group's car remains at the trailhead.

"If you're not totally familiar with it (the area), once you get above timberline, you could get disoriented," Knowlton said.

Knowlton said 15 crew members from La Plata County Search and Rescue and the La Plata County Sheriff's Office, one member of the Upper Pine River Fire Protection District and a Flight for Life are searching the area Monday.