Dylan Redwine, 13, was last seen by his father, Mark Redwine, at 7:30 a.m. Monday at his home in Vallecito, which is about 22 miles northeast of Durango.
Mark Redwine left for Durango and returned home at 11:30 a.m. and Dylan was gone, Dan Bender, a spokesman for the La Plata County Sheriff's Office, said in a news release.
Dylan was staying with his father because of a court-ordered visit and was reportedly upset about the trip.
He moved to Colorado Springs during the summer with his mom and brother.
Bender said the sheriff's office is not ruling out the possibility of an abduction but said Dylan may be a runaway.
Dylan was raised in the Durango area and is known by many people, Bender said. Police are currently interviewing Dylan's family and friends.
Dylan's mother, Eileen, arrived in Durango after Dylan was reported missing. Both parents are cooperating with police, Bender said.
So far three people have reported seeing Dylan since he went missing but none of the reports led authorities to the missing boy.
One person reported that they saw Dylan walking with another boy about his age on Monday afternoon on County Road 501. The sighting was reported to police on Tuesday.
The search area currently includes the shoreline around Vallecito Lake, several small subdivisions in Vallecito, two county roads and the surrounding forest and hiking trails.
Anyone who may have information on Dylan's whereabouts are asked to contact investigators Dan Patterson 505-382-7015 or Tom Cowing 970-382-7045.