Family members and friends of 26-year-old Michelle Le were combing a remote area when the grim discovery was made.
The body was so badly decomposed that investigators were not immediately able to determine if the remains were those of a male or a female.
Le disappeared back in May after taking a break from her studies at a Hayward hospital.
Giselle Esteban, 27, a former friend of Le's from high school in San Diego, has been charged with her murder. Police believe Esteban attacked Le in a Hayward hospital parking garage.
Le was last seen May 27 at the hospital where she was doing a clinical rotation. She had told colleagues she was going to her car. She never returned and her locked Honda SUV was later found a half-mile away.
Esteban told KGO-TV in June that she hated Le because Le was friends with the father of Esteban's 5-year-old daughter. But Esteban denied having anything to do with Le's disappearance.
Police said they found traces of Le's blood inside her SUV and physical evidence that Esteban had also been inside the vehicle, as well as Le's DNA on one of Esteban's shoes.
Esteban is being held without bail and was due back in court Monday.
The Associated Press contributed to this story.