The death of an elderly couple in south central Iowa is being investigated as an accidental carbon monoxide poisoning.

Union County Sheriff Rick Piel says 75-year-old Dale Whitson and 68-year-old Kathy Whitson were found in their home Monday on Spring Valley Lake Drive, about two miles southwest of Thayer. Officials believe both died sometime on Saturday, two days prior to the discovery.

Piel says the investigation is continuing, and that a dual suicide attempt has been ruled out. An official cause of death will come from pending autopsies at the State Medical Examiner’s Office in Ankeny. Piel wasn’t sure when they would take place or when results would be released.