Police in the US have launched an investigation after the veteran actor Gene Hackman was discovered dead in his home on Wednesday.

The body of the 95-year-old - a two-time Oscar winner - was found in his Santa Fe, New Mexico mansion, along with the body of his wife of 34 years, Betsy Arakawa, aged 65, and the body of one of their dogs.

The couple were in separate rooms of the house and appeared to show no signs of external trauma, nor was a suicide note found, although police said that pills were found near Arakawa and the front door to the property was open.

Both human bodies showed signs of "mummification", cops said, suggesting that they could have been dead for weeks - although subsequent investigations have revealed that Hackman's pacemaker stopped working on February 17, some nine days before he was found.

Suggestions that carbon monoxide poisoning could have been responsible for the deaths appeared to be refuted by investigators in a Friday press conference as they said Hackman and Arakawa both tested negative for the gas.

Hackman's daughters Elizabeth, Leslie and Annie said in a joint statement: "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."

Results from the couples autopsies and in-depth toxicology tests to determine their causes of death may not be known for several weeks.