[Updated at 7:49 a.m.: A previous version of this post incorrectly listed Menke's age as 53.]

Menke had gone hiking in the morning, and her friends alerted police after she failed to come home.

Search dogs, an LAPD helicopter and officers from patrol units spent hours in Griffith Park searching for her.

Her locked car was found in a Griffith Park parking lot. Menke's dog was found alive, according to the Los Angeles Police Department.

The sources, who spoke on the condition that they not be named because the investigation was ongoing, said Menke's body was found at the bottom of a ravine near 5600 block of Green Oak Drive.

No cause of death was immediately reported, and it's unclear whether the heat was a factor.

[Updated at 8:42 a.m.: LAPD Lt. Bob Binder said Menke and a hiking buddy set out about 9 a.m. to hike a trail in Bronson Canyon, in the shadows of the Hollywood sign. An hour later, Menke's partner decided to turn back. Menke and her Labrador retriever continued on.

That was the last time she was reported seen. Friends and family contacted authorities about 4 p.m.

First on the scene were officers with the city's General Services Department, which patrols the park. Searchers with the LAPD Metro Division and Los Angeles Fire Department were called in around 6 p.m. Her family and friends aided in the search.

Menke's body was found just after 2 a.m. at the bottom of a ravine near the 5600 block of Green Oak Drive in Bronson Canyon.

Her dog was sitting next to her body, which was about a football field's length from nearby homes.

Ed Winter, assistant chief of the L.A. County coroner's office, said there did not appear to be a jump in deaths Monday because of the extreme heat.

Sources familiar with the death investigation believe Menke became disoriented and collapsed, and the weather conditions contributed to her death. Winter said the coroner's office is trying to determine whether the heat played a role in Menke's death.]

-- Andrew Blankstein

Photos: The scene at the end of Green Oak Drive, where the body of Sally Menke was placed in the coroner's truck. Credit: Al Seib / Los Angeles Times. Below left, Sally Menke Credit: WireImage