Actor Robert Wagner has repeatedly rebuffed efforts by Los Angeles investigators to interview him about his wife Natalie Wood’s death in 1981, an L.A. sheriff's spokesman said.

Detectives have interviewed more than 100 witnesses and gathered new evidence in the 13 months since reopening the inquest into Wood’s death.

Wood was on a yacht off 30 kilometres off Catalina Island with husband Robert Wagner and fellow actor Christopher Walken before somehow ending up in the water.

Actor Robert Wagner, shown in 2002, declined further interviews in the probe of Natalie Wood's death. (Associated Press)

While Walken and yacht captain Dennis Davern have given new statements to police, Wagner has not, an investigator said.

“We reached out through his attorney and got rebuffed,” Sheriff's Lt. John Corina said. "We went to his home, and he refused to talk us, and we sent him a letter, so I say it is fair to say he has declined to be interviewed, repeatedly."

On Monday, the L.A. County coroner’s office announced it had changed the cause of Wood’s death to “undetermined” and noted bruising on her body that indicated she might have been injured before she went into the water and drowned.

Her death originally was ruled to be an accidental drowning, and it was believed she fell off the boat when she went on deck in the middle of the night to secure a dinghy that was banging against the yacht. Everyone on the boat had been drinking at the time of her death.

Wagner was interviewed several times by police in 1981, after her death.

Wagner’s attorney, Blair Berk, released a statement Thursday evening saying that Wagner and his family have fully co-operated with authorities.

“After 30 years, neither Mr. Wagner nor his daughters have any new information to add to this latest investigation, which was unfortunately prompted by those seeking to exploit and sensationalize the 30th anniversary of the death of his wife and their mother,” Berk said in the statement.

The renewed inquiry came after the yacht's captain Davern told 48 Hours and the Today show that he heard Wagner and Wood arguing the night of her disappearance.

With files from The Associated Press