A California woman trying to lay to rest her dead cat stumbled upon the shallow grave of a person, authorities said Monday.

The pet owner in Modesto, California, was digging a hole for her deceased cat on Saturday afternoon when she made the macabre discovery in her backyard, Stanislaus County Sheriff’s deputies said.

An autopsy on the human remains is scheduled for Monday.

“I am going into this with the assumption it's a homicide," sheriff's detective Cory Brown told NBC News, adding that he could not tell from the portion of the body he saw if it was male or female.

The woman who made the discovery has been renting the home for one year and is not considered a suspect, authorities said.

"She (the current renter) was a little bit shaken up; this is not what she expected to see," Brown said.

The property's owner is also not a suspect, police said.

As part of the investigation, detectives are going though the records of several renters who have lived at the house in recent years.

The investigators are also receiving tips from local families who say they have a missing relative. One of those identified as missing vanished about five years ago and lived near the house where the remains were found, Brown said.