ST. JOHNS COUNTY, Fla. -- An autopsy determined that a couple whose bodies were found in their Anastasia Island home on Sunday died of natural causes.

An off-duty firefighter passing the house on Sunday morning noticed an odor coming from the house in the 200 block of Puebla Road in the Treasure Beach neighborhood and found the 80-year-old Donald Hankey and 77-year-old Patricia Hankey dead on the floor of the living room.

St. Johns County officials said the two had been dead for some time -- at least a week -- and that decomposition was quite advanced. Emergency workers were required to use breathing equipment to process the scene.

Preliminary autopsies revealed that both suffered heart attacks, pending toxicology results.

Because they were in poor health and were not running their air conditioning, St. Johns County Sheriff's Office Sgt. Mulligan said that could have contributed to their deaths.