The actor Gene Hackman died from heart disease at his home in New Mexico, most likely a week after his wife, Betsy Arakawa, died from the effects of hantavirus, a disease linked to rodents that can cause respiratory failure in rare cases, the authorities said on Friday.
The revelation that the famous and reclusive couple had died of natural causes put to rest much of the speculation that followed the discovery of their bodies on Feb. 26. But it also raised new questions about the state of mind of Mr. Hackman, who had severe Alzheimer’s disease, and why the couple was not discovered sooner.
Ms. Arakawa, 65, had run a series of errands on Feb. 11, but the authorities could find no evidence of any activity after that, suggesting that she could have died that day. Mr. Hackman, 95, is believed to have died about a week later, on Feb. 18, according to New Mexico’s chief medical examiner, Dr. Heather Jarrell.
Mr. Hackman was found on the floor of the mudroom in the couple’s home, near his cane, while Ms. Arakawa was found on a bathroom floor, beside a counter with pills scattered about. They were not discovered until Feb. 26.
Dr. Jarrell said that the pills found near Ms. Arakawa were thyroid medication and were not associated with her cause of death. She said hantavirus is contracted through exposure to excrement from rodents — in New Mexico, primarily one species of mouse — and it can cause flulike symptoms before progressing to shortness of breath, as well as cardiac and lung failure.
Erin Phipps, a state veterinarian, said the couple’s home had “low risk” of exposure to hantavirus, but that there were signs of rodents in other structures on the property, which is in a secluded neighborhood to the east of Santa Fe.
Sheriff Adan Mendoza of Santa Fe County said Ms. Arakawa had gone to a grocery store on the afternoon of Feb. 11 and was also seen on surveillance video at a pharmacy. She returned to the neighborhood around 5:15 p.m., he said, and she did not respond to emails after that day.
“Based on the circumstances, it is reasonable to conclude that Ms. Hackman passed away first, with Feb. 11 being the last time that she was known to be alive,” Dr. Jarrell said, using Ms. Arakawa’s married name.
Mr. Hackman’s autopsy showed severe heart disease, Dr. Jarrell said, including evidence of prior heart attacks and multiple surgical procedures involving the heart. He tested negative for hantavirus. She said his Alzheimer’s disease was a contributing factor in his death.
The dog that died was an Australian Kelpie mix named Zinna. The dog, who had once been a returned shelter dog, had turned into an “incredible companion under Betsy’s hand,” said Joey Padilla, the owner of a dog boarder and day care company, Santa Fe Tails. Mr. Padilla said he had watched Zinna and Ms. Arakawa’s relationship “flourish” over the years.
Two other dogs, both German shepherds, were found alive on the property.
The surviving dogs, Bear and Nikita, are “healthy and receiving the best care in a familiar environment,” Mr. Padilla said. He said he was waiting to hear from Ms. Arakawa’s lawyer about what to do with them.
Mr. Hackman, a two-time Oscar winner, and Ms. Arakawa, a classical musician who had founded a home goods store in Santa Fe, had rarely been seen in public in recent years, but when they were spotted in their neighborhood, they were often walking their dogs or driving with them in the back.
Neighbors said the couple brightened up when they met a fellow dog lover.
Mr. Hackman and Ms. Arakawa were famously private, living at the end of a cul-de-sac in a gated community known as Santa Fe Summit, east of the city. Their deaths had left their neighbors puzzled and sad.
The police have said that there was no security camera footage from inside or outside the home. They said they would review data from two cellphones found at the house and try to determine when someone last had contact with the couple. The police had said that the key to what happened could be in toxicology results from the bodies.
Sheriff Mendoza said the police had essentially ruled out carbon monoxide, given that both bodies tested negative for the potentially lethal gas.