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Natalie Wood's death certificate has been changed to reflect the lingering questions surrounding her drowning death 30 years ago.

An amended copy, signed on July 26, 2012, but recorded with the Los Angeles County Registrar's Office on Aug. 1, changes the manner of her death from accidental to undetermined, Los Angeles County Sheriff's Department spokesman Steve Whitmore confirmed to ABC News.

Whitmore said the case remains an "open and active investigation."

The cause of Wood's death was changed from drowning to drowning with undetermined factors. The amended document also notes that the actress' body was found "floating on the ocean" under circumstances that were never "clearly established."

Wood died on Nov. 29, 1981, following a party on a boat off California's Santa Catalina Island. Actors Robert Wagner, her husband, and Christopher Walken, her "Brainstorm" co-star, were also aboard the boat.

The Los Angeles County Sheriff's Department reopened its investigation shortly before the 30th anniversary of Wood's death. Nearly eight months later, authorities amended her death certificate.

Members of Wood's family told TMZ in July that the cause of death was revised because some of the bruises on Wood's body were inconsistent with an accidental death by drowning. They said Wood definitely died by drowning, but how she got into the water remains a mystery.

Authorities have said Wagner is not considered a suspect in the case.

ABC News' Jim Vojtech contributed to this report.