The men set out Saturday morning on a hike on Fish Creek Trail, which goes to the summit of Mt. San Gorgonio, according to the San Bernardino Sheriff’s County Department.
They were expected back at their camp Saturday night.
When they never arrived, a fellow camper notified authorities.
The men were identified as David Yoder, Ryan Shankles, and Miguel Delatorre all of Oceanside.
Shankles sister, Niki Shankles Burger, said there were about 60 volunteers on the ground looking for the men.
A helicopter is also searching from the air using an infrared camera, according to Burger, who was posting updates on her facebook page.