Robert Wagner has been named as ''a person of interest'' in the death of actress Natalie Wood - four decades after her passing.

The 87-year-old actor was married to Natalie from 1972 until her death in 1981 and police, who have been re-investigating the case for six years, now know he was the last person to see her before she disappeared.

Speaking in a preview clip from 'Natalie Wood: Death in Dark Water', Los Angeles County Sheriff's Department Lieutenant John Corin told CBS' 48 Hours: ''As we've investigated the case over the last six years, I think he's [Wagner's] more of a person of interest now. I mean, we know now that he was the last person to be with Natalie before she disappeared ... I haven't seen him tell the details that match all the other witnesses in this case. I think he's constantly changed his story a little bit. And his version of events just don't add up.''

Wood was found floating in the water in November 1981 off the coast of Catalina Island in California after spending some time on her family's yacht, the Splendour. She had been with Captain Dennis Davern, Wagner and her friend and fellow actor Christopher Walken. A two week investigation took place at the time, which concluded in the death being ruled as an accident.

However, back in 2011, the Los Angeles County Sheriff's Department reopened the death investigation and a year later, the Los Angeles Coroner's Office altered the death certificate, saying the manner of death was now ''drowning and other undetermined factors''.

And Corin believes Wagner knows ''a lot more about'' Wood's death then what he's said before, adding: ''Well, I think he does because he's the last one to see her.''

Wagner is not and has never been treated as suspect in her death.