A couple found dead in their Utah home remains a mystery. Now police are closing the case.

A couple in their 80s were found dead in their American Fork home in January. Three months later, investigators still aren’t sure how they died — but they are closing the case, police announced Wednesday.

Sally and Duane Francom, both 84, were last seen around mid-November 2023. Officers later discovered the couple dead in their home on Jan. 3 during a welfare check, police said.

The two appeared to have been dead for some time, and seemed to have died around the same time. They were each found in different rooms, though the room Sally was found in showed “possible signs of a struggle,” police said in a news release.

Based on that evidence, as well as the positioning of her body, Sally may have been “killed in a physical altercation,” authorities surmised in a search warrant document warrant obtained by FOX 13.

Relatives also told investigators that Duane was “emotionally and physically abusive,” leading authorities to write in the document that it was “reasonable” to suspect Duane may have strangled Sally before dying of a heart attack “due to the physical stress of strangling someone,” FOX 13 reported.

Police didn’t find any weapons at the scene that may have been used in the deaths. Investigators also didn’t find any “observable indications” of traumatic injury to either of Francoms, according to the release.

The state medical examiner’s office eventually took custody of the Francoms’ remains to conduct autopsies. This week, the office officially ruled their causes of death as “undetermined,” citing the “degree of decomposition.”

“No trauma was found on either body, and no significant amount of carbon monoxide was detected ruling out carbon monoxide poisoning,” police said in a news release, noting the American Fork Police Department has closed the case.

“Both Duane and Sally were found to have heart disease, and toxicology showed nothing suspicious in their blood,” the release continued.

Police said investigators have “no reason to believe” a third party may have been involved in their deaths, as there were no signs of forced entry into their home. It’s why investigators concluded the circumstances surrounding their deaths were “isolated to inside of the home.”

Neither Sally nor Duane Francom appeared to have personal obituaries published after their deaths.