Updated 12:42 p.m: Law enforcement reported the dead body to the Los Angeles County Department of Coroner as a "possible gunshot wound,'' assistant chief coroner Ed Winter said Thursday.
An official familiar with the investigation said shell casings were apparently found at the scene of the crime.
Coroner's investigators were expected to arrive on the scene around noon, he said.
Updated 11 a.m: In a video shot by La Cañada Flintridge Patch editor Donna Evans (above), California Highway Patrol Officer Kevin Denmon said the motorist spotted what he thought was a body just after 5 a.m. in the Angeles National Forest. He made a U-turn, saw it was, in fact, a body, and called 911. Authorities have confirmed it was a male body, but declined to give more details.
Denmon declined to comment on whether shell casings were found at the scene or not.
Angeles Crest Highway three miles north of Foothill Boulevard will likely be closed, in both directions, for several more hours as homicide detectives investigate the area where a motorist found a man's body Thursday morning.
Update 9:15 a.m.: Authorities are waiting on additional investigators to arrive at scene where a man's body was discovered, Sheriff's Homicide Detective Toni Martinez told Patch.
Officials may make a public statement but she indicated that the body is not missing 20th Century Fox distribution executive and former UCLA basketball player Gavin Smith.
Update 8:35 a.m.: The California Highway Patrol identified the body found on Angeles Crest High as a man, according to NBC4.
Shell casings were apparently at the scene of the crime, according to an official at the scene.
Original: A body has been found on Angeles Crest Highway just north of Foothill Boulevard, said Sgt. Debra Herman of the Crescenta Valley Sheriff's Station.
The road has been closed at Angeles Forest Highway and Big Tujunga Canyon Road, she said, noting folks driving in from the Antelope Valley will need to find an alternate route. The road is expected to be closed for several hours.
"We really don't know what's going on at this point, '' Herman said, noting cellular reception is spotty in the area, slowing reports coming in from the field.
LCF Patch is heading to the scene. We'll update this story as more details become available.