US investigators are trying to establish how Oscar-winning actor Gene Hackman and his wife, classical pianist Betsy Arakawa, died after the discovery of their bodies at their home in the US state of New Mexico. Officials said on Friday that evidence points to Hackman having been dead since 17 February - 10 days before the couples' bodies were found. The bodies of the couple and one of their dogs were found by police on Wednesday at their home in Santa Fe, New Mexico, after a maintenance worker called emergency services. Hackman, 95, was discovered in a side room near the kitchen while Arakawa, 65, was found in a bathroom, at the property on Old Sunset Trail in Hyde Park. The couple appeared to have been 'dead for quite a while', said Sheriff Adan Mendoza. Arakawa's body showed signs of 'decomposition', and 'mummification' in the hands and feet, a sheriff's detective said. Hackman's remains 'showed obvious signs of death, similar and consistent' with those on his spouse. A German Shepherd dog owned by the couple was found dead in a bathroom closet near to Arakawa. No cause was given in police statements immediately after the announcement of the deaths. The authorities reported no signs of injury but deemed the deaths 'suspicious enough' to investigate and did not rule out foul play. A carbon monoxide poisoning test came out negative for both Arakawa and Hackman, the Santa Fe Sheriff's office said on Friday. Near Arakawa's head was a portable heater, which the detective determined could have been brought down in the event that she had abruptly fallen to the ground. An autopsy and toxicology tests have been requested for both Hackman and Arakawa. Authorities said it could be a few months before the results of those are released.