Rescue crews are responding to reports of a person yelling for help from over the side of a road on Mt. Baldy, officials said.
Los Angeles County fire officials were called to the area of Mt. Baldy Road and Glendora Ridge in the Bear Flats area shortly before noon, with reports that one or more people were trapped after going over the side of the road.
No one had been found as of 1:30 p.m., county Fire Inspector Scott Miller said.
The response effort included specialized urban search-and-rescue teams and K-9 units.
Sheriff's officials said they received a call regarding someone yelling for help but had no further details.
Flash-flooding killed one person Sunday on Mt. Baldy when his vehicle spilled off a mountain road and into a creek. The man was identified Monday as 48-year-old Joo Hwan Lee of El Segundo.
Crews continued to sweep through the mountain communities Monday to assess the damage. At Mt. Baldy, one home suffered major damage and four sustained moderate damage, said San Bernardino County firefighter Chris Prater.