A search is underway for a teenage girl who was swept into the ocean by a large wave while walking with her family at Treasure Island Beach in Laguna Beach, California.

Her mother and brother were rescued and are in stable condition, while a bystander who helped also needed to be saved from dangerous surf.

Officials have expanded the search using divers, boats, and air support, but the girl has not yet been found.

The incident occurred as Southern California was hit by unusually high surf, with waves reaching up to 10 feet in some areas, the AP has reported.

Authorities say rough conditions are expected to continue before gradually easing.