It was located off a trail near the Griffith Observatory in Hollywood Hills, a popular recreation and tourist area.
“Two dogs were playing with it, and that’s when the dog walkers looked closer and realised it was a human head,” said Los Angeles Police Department spokeswoman Karen Rayner.
The women called park rangers immediately upon finding the head in a bag, Rayner said. Rangers then called the police.
Police believe the severed head had not been at the site for a long time, based in part on the fact that there were no animal bites on it.
Police used cadaver dogs to assist in the search for further human remains until dusk, when they called off the investigation until daylight returns. The crime scene is being guarded by police.