Rescue crews are searching the central Sierra Nevada in California for nine teenagers and two adult hikers who are missing in a rugged area of the mountains.

Fresno County authorities say teens between the ages of 13 and 16 and two 30-year-old adult guides failed to meet up with a third guide as planned on Saturday.

The group is on part of a two-week Outward Bound adventure.

Authorities say a Fresno County Search and Rescue Team are involved in the search, along with volunteer mountaineers, rescuers on horseback and a helicopter.

The search area’s elevation is 9,000 to 10,000 feet.