Legendary actor Gene Hackman and his wife tested negative for carbon monoxide, but what caused their deaths remains unknown, the sheriff leading the investigation said Friday. Hackman likely was dead more than a week before his body was found because his pacemaker last showed activity on Feb. 17, nine days before maintenance and security workers showed up at his home, said Santa Fe County Sheriff Aden Mendoza. The 95-year-old Oscar winner was found Wednesday in an entryway of the couple's Santa Fe home. His wife, Betsy Arakawa, 65, was found lying on her side in the bathroom. A dead German shepherd was found in a kennel near Arakawa, Mendoza said. There were no obvious signs of foul play, and initial autopsy findings “noted no external trauma to either individual,” Mendoza said. The sheriff said he spoke with the pathologist from the New Mexico office of the medical investigator, who said that both Hackman and Arakawa tested negative for carbon monoxide. No cause or manner of death has been determined, and it will be up to the medical investigators to answer many of the questions about when and how the couple died, the sheriff said. Investigators are trying to figure out the last time anyone saw or spoke to the couple who were known to guard their privacy. Authorities released few other details at a Friday news conference about the deaths. According to a search warrant affidavit, an open prescription bottle and pills were on a countertop near Arakawa. Authorities who later searched the home retrieved medication that treats high blood pressure and chest pain, thyroid medication, Tylenol, two cellphones, a monthly planner and records from medical diagnostics testing, court records filed Friday showed. Detectives wrote in a search warrant affidavit that investigators thought the deaths were “suspicious enough in nature to require a thorough search and investigation.” No gas leaks were discovered in and around the home. A space heater was next to Arakawa and may have fallen when she abruptly fell to the floor, according to the affidavit. A maintenance worker who showed up to do routine work at the house could not get inside the house and called a security worker spotted two people on the ground, Mendoza said. The worker who called 911 told an operator he did not know if they were breathing. Hackman was among the most accomplished actors of his generation, appearing as villains, heroes and antiheroes in dozens of dramas, comedies and action films from the 1960s until his retirement in the early 2000s. He met Arakawa, a classically trained pianist, at a California gym in the mid-1980s. They moved to Santa Fe by the end of the decade. Their Pueblo revival home sits on a hill in a gated community with views of the foothills of the Rocky Mountains.