The group, associated with the outdoor adventure program Outward Bound, is made up of teenagers from all over the country -- including a 16-year-old girl from East Palo Alto and a 16-year-old girl from Alameda. One of their guides is a 30-year-old San Rafael man.
Fresno County sheriff's Lt. Mike Lancaster said around 3 p.m. today that the group had been spotted at Florence Lake, in the Red Rock Basin area, by searchers in a helicopter.
"We're sending ground units to the area right now," Lancaster said.
Lancaster said Outward Bound officials are in contact with the group via satellite phone.
"Outward Bound is saying that they're all accounted for and they're all fine," he said.
The group was planning to climb Mount Shinn, which is a few miles from the Burnt Corral Meadow area where they had last been seen, sheriff's Deputy Christian Curtice said.
One of the adult guides told authorities that he had left the group Sunday to go see if the mountain was passable. They had agreed to meet back up at Red Rock Basin later in the day, Curtice said.
The guide hiked Mount Shinn and then headed to the meeting spot, but the group wasn't there.
The guide then searched the area for two days before contacting Outward Bound. Outward Bound staff then contacted the sheriff's office, which began looking for the group in a 30-square-mile area to the north and east of Courtwright Reservoir. The elevation in the area is about 9,000 to 10,000 feet.
The group had set out from the Maxon Trailhead on Sunday prepared for a two-week backpacking and climbing excursion, Curtice said.
Search and rescue teams made up of 35 sheriff's office personnel on foot, horseback, in jeeps and in a helicopter expanded the search area to 90 square miles this afternoon, Curtice said.
The sheriff's office set up a command post at the reservoir, where some of the teens' family members had begun to gather, Curtice said.
Outward Bound officials did not immediately return phone calls seeking comment.