Through three decades of fevered tabloid speculation and whispers of a deeper story, the official account never changed: Natalie Wood drowned accidentally.

The 43-year-old star of “West Side Story,” who couldn’t swim, had been drinking the night before she was found floating face-down in frigid waters off Santa Catalina Island.

When the L.A. County Sheriff’s Department reopened the case in November 2011, around the 30th anniversary of her death, skeptics questioned the timing and doubted whether there was anything new to be learned.

Instead of quieting speculation, however, the investigation has raised fresh — and probably unanswerable — questions about one of Hollywood’s most enduring puzzles.

In a report released Monday, the coroner, Lakshmanan Sathyavagiswaran, questioned the original 1981 findings and changed Wood’s cause of death from “accidental drowning” to “drowning and other undetermined factors.”

The coroner’s report cited unexplained fresh bruising on the actress’ right forearm, left wrist and right knee, along with a scratch on her neck and a superficial scrape on her forehead.

Officials said the wounds open the possibility that she was assaulted before drowning.

“This Examiner is unable to exclude non-accidental mechanism causing these injuries,” the report said, adding that evidence suggested the bruising occurred before Wood entered the water.

Sheriff’s investigators said that the Wood case remains open but that detectives have reached an impasse.

One law enforcement source who has worked on the case said detectives may never have a conclusive answer given that “evidence is stale — with fading memories and incomplete forensics.”

The source, who spoke on the condition of anonymity because the case is ongoing, said there was not enough evidence to classify the case a crime, much less a homicide.

Experts said it was highly unusual for coroners to contradict the autopsy findings performed by their own office.

Michael Baden, a former New York examiner and noted trial expert witness, said that although both examinations of Wood’s body looked at the same evidence, the new report found the bruising to be far more significant — enough to change the cause of death.

“Sathyavagiswaran knows by issuing this opinion that he will unleash criticism on his predecessor and questions over how it handled a celebrity death three decades ago,” Baden said. “He knows in saying this he has criticized [former coroner] Dr. [Thomas] Noguchi and the office back in 1981.”

Noguchi did not return calls for comment.

The new report noted “conflicting statements” about when Wood disappeared, and whether she had argued with her husband, actor Robert Wagner, who — along Christopher Walken, her co-star in the film “Brainstorm” — were aboard the 60-foot yacht where she was last seen alive Nov. 28, 1981.

Hours before her death, authorities said, the three actors had had dinner at Doug’s Harbor Reef restaurant and then returned to the yacht, called the Splendour, where they drank and an argument ensued between Walken and Wagner.

According to the new autopsy report, Wood went missing about midnight, and an analysis of her stomach contents placed her death around that time. The report said Wagner placed a radio call to report her missing at 1:30 a.m.

Roger Smith, the L.A. County rescue boat captain who helped pull Wood’s body from the water, said he did not receive a call to look for her until after 5 a.m.

The original investigators believed Wood sustained her bruises after falling off the yacht and struggling to pull herself from the water into a rubber dinghy, whose starboard side bore scratch marks that seemed consistent with that theory.

But in his report, Sathyavagiswaran noted that investigators did not take nail clippings from Wood’s body to determine whether she had made the scratch marks, and the dinghy was no longer available to be examined.

The coroner believes Wood died soon after entering the water.

In an interview Monday, Smith said he wondered whether Wood might have been found alive if the rescue effort had gotten underway sooner.

“There’s no question in my mind that he just delayed calling for us,” Smith said, referring to Wagner.

Smith said he and a deputy examined Wood’s body but saw no bruises.

“We went over her very closely,” said Smith, 68. “When we looked at her, we didn’t see any bruises. We were looking for needle marks or anything like that — we didn’t see anything.”

He said the cold water may have delayed any bruising.

Smith said he examined the dinghy, which was found beached nearby, and saw dislodged seats and what appeared to be “nail marks along the inside of the raft,” as though Wood had tried frantically to reach in and pull herself up.

“She probably couldn’t pull herself in because she was so weak,” Smith said. “It looked like she was maybe grabbing things. I just think she was trying to get in.”

Smith said he had doubted an earlier claim by yacht captain Dennis Davern that he had seen bruises on Wood’s body.

“He could not have seen bruises on her because out of decency, I covered her up with a disposable blanket,” Smith said.

Wagner has said his wife hadn’t been suicidal and called her death a tragic accident.

According to the account given by Wagner’s spokesman, when he noticed his wife missing he believed she had taken the dinghy, and he went looking for her after 10 to 15 minutes, then contacted the Harbor Patrol when he couldn’t find her.

Wagner could not be reached for comment Monday.

“I have gone over it so many millions of times with people,” Wagner told The Times in 2008.

-Los Angeles Times