Natalie Wood's death certificate was changed in late June from "Accident" to "Undetermined," TMZ reported.
According to TMZ, the L.A. County Coroner filed the documents late last month and informed Wood's family of the change. Detectives said the change was made in part due to bruises on Wood's body that were inconsistent with death by drowning.
Wood died November 29, 1981 after an alcohol-fueled party on a boat off Catalina with Robert Wagner and Christopher Walken on board.
Family members were told that authorities cannot definitely prove Wood's death was an accident or due to foul play, TMZ reported.
According to the report, Wood's death was definitely due to drowning, but the manner in which she ended up in the water is unknown.
The investigation is still active.