Police officials say actor Gene Hackman and his wife may have been dead for some time and the cause of death has yet to be revealed.
Investigators in Santa Fe, New Mexico, have not said whether they have determined the cause of death.
No foul play was suspected, authorities said, though a search warrant showed investigators thought the deaths were "suspicious enough in nature to require a thorough search and investigation.”
The New Mexico Gas Co. tested gas lines at the home but didn't find any signs of problems at the time, according to the warrant.
An investigator noted people may not show sings of poisoning if they are exposed to gas leaks or carbon monoxide, but also there weren't signs of a leak.
Results of autopsies conducted on both bodies were not available Thursday, authorities said.
Hackman, 95, his 63-year-old wife, Betsy Arakawa, and their dog were found dead in different rooms of their Santa Fe home on Wednesday.