Trethaway had apparently gone skiing alone in the backcountry Sunday and failed to return.
"We would also like to remind anyone using the backcountry, especially this time of year, of the importance of telling someone where you intend to go, how long you plan to stay, and how many persons are in your party," Lovell said in a prepared statement.
At about 9:25 a.m. Monday, searchers found clothing and equipment believed to be the property of Trethaway. Additional resources were committed to the area, and with the help of a search dog the remains of Trethaway were located. His body was removed from the area and next of kin were notified, Lovell added.
Authorities said Trethaway's car was earlier found by the Bayview Trailhead near Emerald Bay.
About 60 searchers were deployed, including members from the El Dorado County Search and Rescue unit, Placer County Sheriff's Office, Douglas County Sheriff's Office, South Lake Tahoe Police Department, Lake Valley Fire Department, Fallen Leaf Fire Department, Meeks Bay Fire Department, Tahoe Nordic Ski Team, California State Parks and the California Rescue Dog Association.