SPANISH FORK, Utah -- A tenant found human remains buried in the backyard storage cellar of a Utah home where a woman who went missing nearly three decades ago once lived, reports CBS affiliate KUTV.

Police say 28-year-old Peggy Sue Case was reported missing from the Spanish Fork home in 1988. On Monday, a tenant living there noticed sagging in the cellar's dirt floor and decided to dig with a friend, curious because he heard from a neighbor about Case's disappearance, reports the Salt Lake Tribune.

The two uncovered an apparent human skull wrapped in a blanket and plastic mesh, buried about 18 inches deep, according to the paper. They called police around 10:15 a.m.

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The skull will be taken to the medical examiner's office for identification.

According to the Salt Lake Tribune, Case's boyfriend Michael Kufrin is considered a person of interest in the disappearance, which Spanish Fork police say was extensively investigated. The couple lived together at the home when Case was last seen at a hot-tub party they both attended on July 9, 1988 in Payson, the paper reports.

Police said they suspected foul play, but had no evidence of a crime.

Spanish Fork detective Carl Johnston told the paper witnesses reported hostility between the two when Johnston accused Case of flirting with some men at the party. The two left together, and Case was never seen again. Kufrin reportedly called Case's workplace to report her sick after the party, and the next day told Case's employers she had gone out of town to buy a car.

Suspicious because the behavior was unlike her, co-workers reported Case missing July 15, 1988. Kufrin initially claimed Case was staying in contact with him by phone, but he later stopped cooperating with police. He reportedly served time in an unrelated attempted theft case before moving back to his home state of Illinois, according to the Tribune.

Johnston, who initially investigated the disappearance, told the Tribune that if the remains are identified as Case, "that's a great thing for her family to have some closure." Case's remains would "add some new light on some of the elements" already discovered by police, Johnston told the paper.

Police say they know where Kufrin may be and they want to talk to him.

Investigators say that police dug through the soil in the cellar shortly after her disappearance, but didn't find any evidence.