Update, 6:15 p.m.: Authorities were unable to find any injured hiker up near Mystic Canyon Trail after Glendora Police received a report of someone yelling for help, deputies said.
Rescuers from the San Dimas Sheriff's Mountain Rescue Team also searched other trails, including Colby Trail, but no victim was located, said a watch sergeant with the San Dimas Sheriff's Station.
PREVIOUSLY: Authorities have been searching for over an hour after they received a report of a hiker yelling for help somewhere in the area of Mystic Canyon Trail, Friday afternoon.
Deputies received the call around 2:16 p.m.
The San Dimas Sheriff's Station has activated its mountain rescue team to aid in the search near Big Dalton Canyon Road and Glendora Mountain Road, said Lieutenant David Vega of the San Dimas Sheriff's Station.
Two units from the Los Angeles County Fire Department have also responded, an official said.
Fire fighters also used a helicopter to search Mystic Canyon Trail by air, but have so far found no one, according to Sheriff's broadcast traffic.
This story will continue to be updated as information becomes available.
