Oscar-winning actor Gene Hackman died of natural causes, probably around a week after his wife passed away, the chief medical investigator in the US state of New Mexico said Friday.

The findings end more than a week of mystery that have surrounded the death of one of Hollywood's most beloved stars, whose everyman persona belied a powerful presence and rare acting skill.

"The cause of death for Mr. Gene Hackman, aged 95 years, is hypertensive and atherosclerotic cardiovascular disease, with Alzheimer's disease as a significant contributory factor," Heather Jarrell, the chief medical examiner for the New Mexico Office of the Medical Investigator, told reporters.

"The cause of death for Miss Betsy Hackman, aged 65 years, is hantavirus, pulmonary syndrome. The manner of death is natural."

Neither body showed any sign of trauma, nor any indication of carbon monoxide poisoning, which had been an initial suggestion.

Hantavirus presents as a flu-like disease, with symptoms including fever, muscle aches, cough, sometimes vomiting and diarrhea that can progress to shortness of breath and cardiac or heart failure and lung failure, Jarrell said.

"This occurs after a one- to eight-week exposure to excrement from a particular mouse species that carries Hantavirus."

Jarrell said data from Hackman's pacemaker showed its last activity over a week before his body was found when maintenance workers were unable to access their sprawling Santa Fe property.

"Based on this information, it is reasonable to conclude that Mr. Hagman probably died around February 18. Based on the circumstances, it is reasonable to conclude that Miss Hackman passed away first, with 11 February being the last time that she was going to be alive," said Jarrell.