Authorities have discovered new information changing the timeline of when they believe Academy Award-winning actor Gene Hackman and his wife, Betsy Arakawa, died.

The couple were found dead in their New Mexico home last month with officials saying the pair had been dead for some time before they were discovered by neighbourhood security.

Officials initially said they believed Arakawa died on 11 February and Hackman died one week later.

The Santa Fe County Sheriff's Office now says they have confirmed that Arakawa made multiple calls to a health clinic on 12 February for medical treatment, which the clinic told BBC she never was able to receive.

The sheriff's office said they learned of the calls when they received cell phone data from her phone.

They said there were three calls made that morning to Cloudberry Health, a personalized concierge medical practice in the area. She received a fourth call, also from the clinic.

The sheriff's office noted it never reported an official date of death for her and said that initially, they'd stated that Arakawa's last known activity was on 11 February.

Authorities say she'd exchanged emails with a massage therapist and visited a grocery store, pharmacy and a pet store. Garage clicker data showed she returned home around 5:15 p.m. that day.

Dr Josiah Child, who leads Cloudberry Health, told the BBC that while the clinic had never treated Hackman or Arakawa, she had reached out for medical advice.

"She called and described some congestion but didn't mention any respiratory distress, shortness of breath, or chest pain," he said.

Arakawa initially had scheduled an appointment for 12 February but cancelled on 10 February, explaining that she needed to care for her husband, Dr Child said.

On the morning of 12 February, she called again seeking treatment but because no doctor-patient relationship had been established, the clinic told her she needed to be seen in person.

"There were a couple calls back and forth to just schedule that appointment for the afternoon, but she never showed up," Dr Child explained.

"Our office called back several times and never got an answer."

The couple were both found dead on 26 February.

Chief Medical Investigator Dr. Heather Jarrell stated that "based on the circumstances, it is reasonable to conclude that [Betsy] passed away first."

The Santa Fe medical examiner determined she died from hantavirus pulmonary syndrome, a rare rodent-borne respiratory disease.

Authorities believe Hackman died on 18 February - the date of his last recorded pacemaker activity, which showed an abnormal rhythm of atrial fibrillation.

His cause of death was severe heart disease, with advanced Alzheimer's disease listed as a contributing factor. Experts believe his Alzheimer's may have prevented him from realising his wife of more than 30 years was dead in the home where he was living.

If he did, experts told the BBC, he likely went through various stages of confusion and grief, trying to wake her up before the disease caused him to become distracted or too overwhelmed to act - a process that likely repeated for days before he, too, died.

A necropsy report also revealed that one of the couple's three dogs, which had been crated while recovering from surgery, died from starvation and dehydration.

As the investigation continues, representatives for Hackman and Arakawa's estate have taken legal action to block the release of body camera footage and other visual evidence from their home when their remains were discovered.

A New Mexico judge has issued a temporary restraining order that prevents their release, with a hearing set for March 31.