Gene Hackman and his wife, Betsy Arakawa, tested negative for carbon monoxide poisoning officials said Friday as they continue to investigate what caused the couple's deaths.

Santa Fe County Sheriff Adan Mendoza told NBC's “Today” show that investigators were trying to sort out conflicting stories about the doors. He said several doors were unlocked and a rear door was open, which allowed two dogs that survived to go in and out. He also said he thinks the front door was closed but unlocked.

The bodies of Gene Hackman and his wife, Betsy Arakawa, both tested negative for carbon monoxide poisoning. Hackman's pacemaker stopped Feb. 17.