US actor Gene Hackman and his wife Betsy Arakawa could have been dead for days or even weeks when investigators found their bodies, according to a Santa Fe County sheriff.
Sheriff Adan Mendoza, speaking to US network NBC's Today show on Friday, said investigators are now trying to work out the last time the pair were seen.
He said finding out who they spoke to last was "a challenge because they were very private individuals" and added that post-mortem examination results could take months.
Oscar-winning film star Hackman, 95, and his wife, 65, were found dead, along with one of their dogs, at their home in Santa Fe, New Mexico, on Wednesday, and police said there were no apparent signs of foul play.
Mr Mendoza told Today there were several conflicting stories about which doors were locked at the house - he said several were unlocked and a rear door was open, which allowed two dogs that survived to go in and out.
He also said he thought the front door was closed but unlocked.
An inventory from the search of the couple's home said that a pill bottle had been found open, with pills scattered next to Ms Arakawa.
It comes after preliminary findings from a medical investigation found Hackman and his wife suffered "no external trauma".
A statement from the Santa Fe County Sheriff’s Office said: "In the early hours of Thursday, Hackman and Arakawa were transported to the Office of the Medical Investigator (OMI).
"An autopsy was performed. Initial findings noted no external trauma to either individual."
The official results of the post-mortem examinations and toxicology reports are pending and the manner and cause of death have not yet been determined, according to the Sheriff's Office.
Two other dogs were found alive at the property, one inside and one outside.
The alarm had been raised by a maintenance person doing pest control at the property, who was concerned because he had not seen the couple, police said.
New Mexico Gas Company tested gas lines in and around the home after the bodies were discovered, according to a search warrant, and while no signs of problems were found, a detective noted that people exposed to gas leaks or carbon monoxide may not show signs of poisoning.
Carbon monoxide and other toxicology test results are pending.
While there was no "immediate" evidence of foul play, detectives confirmed the investigation was in its "preliminary" stages.
"There was no indication of a struggle," Mr Mendoza told the media.
"There was no indication of anything that was missing from the home or disturbed that would be an indication that there was a crime that had occurred."
In a 911 call, a maintenance worker said he was unable to get inside the house when asked if the people inside were breathing.
"I have no idea," he said.
"I am not inside the house. It’s closed. It’s locked. I can’t go in. But I can see she’s laying down on the floor from the window."
Hackman’s body was found in a mud room, and his wife was found next to a space heater in a bathroom, detectives said in the warrant.
Hackman’s daughters Elizabeth and Leslie, and his granddaughter Annie, said they will miss the actor "sorely" and are "devastated by the loss".
A statement to the PA news agency said: "It is with great sadness that we announce the passing of our father, Gene Hackman and his wife, Betsy.
"He was loved and admired by millions around the world for his brilliant acting career, but to us he was always just Dad and Grandpa. We will miss him sorely and are devastated by the loss."
Hackman and his wife, a classical pianist, married in 1991.
Hackman was a Best Actor Oscar winner in 1972 for his iconic role as the detective Jimmy 'Popeye' Doyle in William Friedkin's The French Connection.
He won the Best Supporting Actor Oscar in 1993 for his role as the villainous sheriff 'Little' Bill Daggett in the Clint Eastwood western Unforgiven.
Born in San Bernadino, California in 1930, Eugene Alder Hackman served in the US Marines - lying about his age to enlist.
He served from 1947 to 1952 as a field radio operator and then as a broadcast journalist. He went on to study journalism and television production at the University of Illinois but later pivoted to pursue an acting career at the age of 30.
He was a friend and classmate of future co-star Dustin Hoffman at the Pasadena Playhouse in California - where they were voted 'The Least Likely to Succeed' by their fellow pupils.
Hackman and Hoffman moved to New York to further their careers, befriending and living with another future Oscar winner - Robert Duvall as they tried to get a break.
After bit parts and Off-Broadway roles, Hackman made his Broadway debut in Children from Their Games in 1963. Broadway success followed in 1964's Any Wednesday with Hackman's big-screen break coming in the film Lillith in the same year.
He was Oscar-nominated for Best Supporting Actor in 1967's Bonnie and Clyde, the film that brought him to a wider audience around the world. Another Best Supporting Actor nomination followed for 1970's I Never Sang for My Father.
Then came the role in 1971 that made him a star - Jimmy 'Popeye' Doyle in The French Connection.
Ironically, director Friedkin felt Hackman was not right for the part of Doyle, and numerous other actors were considered before Hackman was eventually cast.
Among his many other screen credits were The Conversation, The Poseidon Adventure, French Connection II, Superman and its sequels, Mississippi Burning, The Firm, and The Royal Tenebaums.
Among Hackman's other honours were BAFTA awards for Best Actor for The French Connection/The Poseidon Adventure and Best Supporting Actor for Unforgiven; Golden Globes for The French Connection, Unforgiven, and The Royal Tenenbaums; and the Berlin International Film Festival's Silver Bear award for Mississippi Burning.
Reflecting on his career in an interview with Terry Wogan on BBC One's Wogan in 1986, Hackman said: "I never had any large goals as an actor. All I wanted to do was work. I loved it so much..."
Living outside Santa Fe, New Mexico, Hackman was married twice and had three children - Christopher, Elizabeth Jean and Leslie Anne - with his late ex-wife, Faye Maltese, who died in 2017. He married Ms Arakawa in 1991.
Additional Reporting: Press Association, Reuters, AFP
