An autopsy was scheduled for Saturday morning on the remains of a white female discovered frozen to the ground in a field on Chicago's southwest side, the Cook County medical examiner's office said.

The find immediately sparked speculation the remains could be those of 24-year-old Stacy Peterson, who was reported missing Oct. 29 after she failed to show up at a friend's house.

Pam Bosco, spokeswoman for Peterson's family, told FOXNews.com police are 99 percent sure it is not her.

However, they are holding off saying for certain that it is not her until after the autopsy.

Police said a suburban land surveyor found the badly decomposed remains on Friday afternoon while taking soil samples.

Police said the woman appeared to have light-colored red or blonde hair. Authorities said the worker found a human foot and leg near a blue garbage can, but Chicago police said they did not find the blue garbage can.

Authorities said the body was found about 100 feet from a set of train tracks just south of the Chicago Sanitary and Ship Canal.

Peterson has two children with her husband, Drew Peterson, who is a suspect in her disappearance.

The Associated Press contributed to this article.