Fifty years have passed since she died, but there is still a shroud of mystery surrounding the legendary Ms. Marilyn Monroe.

While she might still be one of Hollywood's most recognizable sex icons, Monroe remains an elusive figure, having been found dead in her Los Angeles home in 1962 at the young age of 36.

"In the end, Monroe is one of the most complex female public figures in American history, and that real complexity plays a role in her continuing ability to fascinate us," author of "Marilyn: The Passion and the Paradox," Lois Banner, wrote for the Los Angeles Times. "We admire her beauty, puzzle over her mysteries and see her as a reflection of the quixotic, multifaceted, always striving and often contradictory American character."

Banner believes that the end of Monroe's story sums up the tale in and of itself. "She loved to live in a mysterious way," he told USA Today.

So, who was the real Marilyn Monroe?

Those who knew her said she was often misunderstood. She was not the dumb blonde she might have portrayed in her films. She was smart and driven, and she could even be unprofessional and exasperating to work with, according to a feature in the Los Angeles Times.

"She was trying to prove she was a serious actress and not just a movie star playing bimbo parts," Don Murray, who starred alongside Monroe in the 1956 drama "Bus Stop," told the Los Angeles Times. Yet, despite her desire to come off as professional, she would often forget her lines. "That was very strange, that lack of discipline," he added. "She was a very experienced film actress, but she could forget so many of the mechanical techniques. She would constantly miss her marks so she would be out of focus or out of the light or in a shadow. I think it was a lack of confidence. For somebody who the camera loved, she was still terrified of going before the camera and broke out in a rash all over her body."

Monroe was known as a bodacious bombshell who oozed confidence and charisma. Off-camera, however, her psychological state was frail. Her love life was a continuous roller coaster and she dealt with bouts of depression.

In his book, Banner alleges that Monroe might have been a lesbian.

"How could she be the world's heterosexual sex goddess and desire women?" writes Banner in an excerpt published by The Guardian. "How could she have the world's most perfect body on the outside and have such internal imperfections? Why was she unable to bear a child? The adult Marilyn was haunted by these questions."

By various accounts, the movie star also struggled with depression. In the days before her death, she was reportedly having a particularly difficult time, according to The Telegraph.

Monroe's death is one of the greatest mysteries woven into her legend.

Her death had been ruled a "probable suicide," but those who knew her found it hard to believe she would kill herself, according to a new article in People magazine. Forensic pathologist Cyril Wecht told People he has "a strong suspicion she might have been injected."

The plot thickens with news that the FBI files on her case, which were filed under "Foreign Counterintelligence," are missing, according to CBS News. The Associated Press attempted to obtain a complete record of the FBI's monitoring of the superstar under the Freedom of Information Act, but to no avail. The FBI no longer has them, nor does the National Archives.

"On the basis of my own involvement in the case, beginning with the autopsy, I would call Monroe's suicide `very probable,"' wrote Dr. Thomas Noguchi in his 1983 memoir, "Coroner." "But I also believe that until the complete FBI files are made public and the notes and interviews of the suicide panel released, controversy will continue to swirl around her death."

Mystery may forever surround Ms. Monroe -- but that may be exactly how she intended it to be.

"I knew I belonged to the public and to the world," Monroe is quoted as saying in the "Unfinished Biography of Marilyn Monroe," "not because I was talented or even beautiful but because I had never belonged to anything or anyone else."

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  • In this undated publicity photo courtesy Running Press, Marilyn Monroe is shown wearing a knife-pleated gold lamé gown made from

  • FILE - In this 1946 file image taken by photographer Joseph Jasgur and released by Julien's Auctions, Norma Jean Dougherty, who eventually changed her name to Marilyn Monroe, is shown. Copyrights and images from Marilyn Monroe's first photo shoot sold for $352,000 at Julien's Auctions after a bankruptcy judge in Florida ruled that photos taken of Monroe were to be sold at auction in Dec. 2011 to settle the debts of the photographer. (AP Photo/Julien's Auctions, Joseph Jasgur, File)

  • Marilyn Monroe

    In this image released by Beverly Hills Collection, actress Marilyn Monroe is seen at The Beverly Hills Hotel. The Beverly Hills Hotel is celebrating its 100th Anniversary in May. (AP Photo/Beverly Hills Collection)

  • FILE - In this 1953 publicity file photo provided by Running Press, Marilyn Monroe is shown on set in the film, "Gentlemen Prefer Blondes." Monroe is probably best remembered for her comic turns in this film. The picture is included in a new 2012 book, "Marilyn in Fashion," published by Running Press. (AP Photo/Courtesy Running Press)

  • FILE - In this 1959 file photo provided by United Artists, Tony Curtis, left, and Marilyn Monroe are shown in the hilarious, milestone comedy, "Some Like It Hot," produced, directed, and co-scripted by Billy Wilder. (AP Photo, File)

  • In this undated publicity photo courtesy Running Press, Marilyn Monroe is shown in the first photo taken of her in the famous white dress from the "The Seven Year Itch." For a brief scene in "The Seven Year Itch," in September 1954, her character strolls on a Manhattan street on a stifling summer evening. When a subway rattles beneath her, Marilyn stands astride a sidewalk vent to catch a cool breeze that swirls her skirt up around her waist. (AP Photo/Courtesy Running Press)

  • A South Korean man is reflected on a frame of a photo of late U.S. actress Marilyn Monroe during her photo exhibition at a department store in Seoul, South Korea, Friday. June 8, 2012. (AP Photo/Ahn Young-joon)

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  • Description Promotional photograph of actor <span class='searchmatch'>Marilyn</span> <span class='searchmatch'>Monroe</span> (1950s) | Source http://www. art. com/gallery/id--0/posters. htm? <span class='searchmatch'>marilyn+monroe</span> | <b>...</b>

  • Photo Caption: <span class='searchmatch'>Marilyn</span> <span class='searchmatch'>Monroe</span> appearing with the USO Camp Show, "Anything Goes," poses for the shutterbugs after a performance at the 3d <b>...</b>

  • FILE - In this Sept. 9, 1954 file photo, Marilyn Monroe poses over the updraft of a New York subway grating while in character for the filming of "The Seven Year Itch" in New York. Monroe's flirty dress from "The Seven Year Itch" is going to a collector who bid $4.6 million at a weekend auction of Hollywood memorabilia. The dress was among the film costumes and props collected by Debbie Reynolds over four decades. (AP Photo/Matty Zimmerman, File)

  • FILE - In this September 15, 1954 publicity photo courtesy Running Press, Marilyn Monroe is shown during the

  • Marilyn Monroe

    FILE- This April 1962 file photo shows actress Marilyn Monroe on the set of "Something's Got To Give," in Los Angeles. In the Hollywood landscape of new, new, new, what really stands out on the red carpet is that today's starlets still emulate the looks of classic screen beauties, including Elizabeth Taylor, Marilyn Monroe and Rita Hayworth, who ruled the red carpet in the 1950s. (AP Photo/File)

  • **FILE** Clark Gable and Marilyn Monroe, play a scene in "The Misfits" in this undated file photo. It turned out to be the last movie for both in 1961. (AP Photo, file)

  • Picture dated of the fifties showing American actr

    SAN FRANCISCO, UNITED STATES: Picture dated of the fifties showing American actress Marilyn Monroe (R) with her husband baseball legend Joe DiMaggio. (Photo credit should read AFP/AFP/Getty Images)

  • American actress Marilyn Monroe poses in 1959 for

    NEW YORK CITY, UNITED STATES: American actress Marilyn Monroe poses in 1959 for the photographers at La Guardia Airport before to fly to Chicago, for the presentation of her film 'Some like it hot'. (Photo credit should read STR/AFP/Getty Images)

  • Undated photo shows US actress Marilyn M

    Undated photo shows US actress Marilyn Monroe a few weeks before she died in 05 August, 1962 at the age of 36. The circumstances of her death have never been cleared up. AFP PHOTO (Photo credit should read STR/AFP/Getty Images)

  • The crypt of Marilyn Monroe is seen at t

    The crypt of Marilyn Monroe is seen at the Westwood Village Memorial Park Cemetery in Los Angeles August 3, 2012. August 5th will be the 50th anniversary of the mysterious death of the Hollywood legend. AFP PHOTO / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/GettyImages)