Thurston County Coroner Gary Warnock says he was notified of the find about 10 a.m. as sheriff's deputies continue searching around an old fish hatchery in a wooded area along the Nisqually River.
All the body parts have been found within a mile of each other and may have been scattered by animals.
The search began after a dog brought a leg to its owner, 93-year-old Bill Flowers, on Nov. 5. Flowers said the leg was gray in color, and was dismembered about 4 inches from the buttocks.
He buried the leg in his backyard, and didn't call police until four days later - at the urging of his daughter - because he was scared he might be accused of murdering the person.
Search and rescue dogs were brought and found more remains - a rib cage, pelvis and part of a skull, including a jawbone with teeth.
The parts appear to come from the same person. Judging by the size, it was an adult, not a child, Warnock said.
But the coroner was unable to say whether it was a man or woman, how long ago the person died and how the body was dismembered.
The leg and foot was to be examined later Wednesday by a pathologist who might be able to say whether the body was cut with tools or pulled apart by scavenging animals.
All the body parts were being sent to the King County medical examiner's office in Seattle on Thursday for study by an anthropologist who might be able to determine age, sex and height.
They'll also try to reconstruct the skull for any sign of injuries, Warnock said. There's no proof now of a crime, he said.
It's unknown yet whether there are fingerprints or dental records that could be used to identify the body.
"Everybody in the community was a little nervous when they first heard about the body," said Willie Frank III, vice-chairman of the Nisqually Indian Tribe.
Frank said he is not aware of anyone who was reported missing from the reservation but the incident still has some residents feeling unsettled.
"For some of our elders, who aren't able to get around very well, they're very scared," he said. "We don't want to see this in Nisqually. This isn't good for our tribe. This isn't good for our community. This isn't good for Thurston County."