Hollywood star Robert Wagner has been named a "person of the interest" over the death of actress Natalie Wood.

Wood, who was twice married to the Austin Powers actor, drowned in southern California in 1981.

Shortly before her death she had been on a boat trip with her husband and fellow Hollywood heavyweight Christopher Walken.

Speculation around the events has grown in recent years and two investigators from Los Angeles County Sheriff's Department labelled 87-year-old Wagner a "person of interest" on Thursday.

At the time a coroner ruled Wood's death the result of accidental drowning, but this was revised in 2012 to "drowning and other undetermined factors".

The development comes ahead of a programme called "48 hours" which is set to be aired on Saturday.

Snippets from the show have been broadcast by CBS News.

In the US, a "person of interest" refers to someone who is believed to possess information that would help investigators but has not been arrested and is not necessarily a suspect.

Wood's body was found floating in a Santa Catalina Island cove on the morning of Nov 29, 1981, after a night of dining and drinking on a yacht with Wagner, Walken and the captain.

The 43-year-old was said to have a lifelong fear of drowning and dark water.

Her body was found dressed for bed in a long nightgown and socks but wearing a red jacket over her nightclothes.

"As we've investigated the case over the last six years, I think he's more of a person of interest now," a detective told CBS News.

"I mean, we know now that he was the last person to be with Natalie before she disappeared."

She said that Wagner's has shifted over the years "and his version of events just don't add up".

"She looked like a victim of an assault," another detective said.

Wood was known for her roles in Miracle on 34th Street (1947) and West Side Story (1961).

She was married to Wagner between 1957 and 1962 and from 1972 until her death.

Wagner has refused to comment.