KTLA-TV, Los Angeles, said that Nicholas Cendoya, 19, and Kyndall Jack, 18, contacted authorities Sunday at 8:30 p.m. asking for help. The pair told police they believed they were one mile away from their car, but couldn't find their way back.
Police located the car but have not found any sign of the hikers, and the teens' cell phone battery died before authorities were able to get an accurate GPS location.
The search has been concentrated near Holy Jim Canyon after a tracking dog picked up a scent there.
Authorities said they believe the teens are still alive.
Hundreds of friends and family joined in the search Tuesday, KTLA-TV said.