Micah True, a mythic figure among extreme-distance runners, went for a 12-mile run Tuesday morning and has yet to return, setting off a search in the Gila Wilderness of southwestern New Mexico.

“We had an initial report that he was seen on Highway 15, heading north, but we have no other clues whatsoever,” said Bob Rodgers, the search and rescue resource officer for the New Mexico State Police. “We thought we had found some of his tracks at one time but that turned out to be someone else.”

Highway 15 leads to the Gila Cliff Dwellings National Monument, the ancient homes of the Mogollon people who lived in the area’s steep canyons 700 years ago. It was the type of terrain True favored.

True, 60, was a central character in the best-selling nonfiction book “Born to Run” by Christopher McDougall. He was described as a man who overcame injuries after learning a new way to run from Mexico’s Tarahumara Indians, who are renowned for their running skill over long distances. True excelled at distances of 50 miles or more over steep and rocky trails, commonly running in sandals.