Singer and songwriter Sixto Rodriguez, who became the subject of the Oscar-winning documentary "Searching for Sugarman," died Tuesday in Detroit. He was 81.

Rodriguez' death was announced on the Sugarman.org website and confirmed Wednesday by his granddaughter, Amanda Kennedy.

A 2013 Associated Press story referred to Rodriguez as "the greatest protest singer and songwriter that most people never heard of."

His albums flopped in the United States in the 1970s, but unbeknownst to him, he later became a star in South Africa where his songs protesting the Vietnam War, racial inequality, abuse of women and social mores inspired white liberals horrified by the country's brutal racial segregation system of apartheid.

Swedish filmmaker Malik Bendjelloul's documentary "Searching for Sugar Man" presented Rodriguez to a much larger audience. The film tells of two South Africans' mission to seek out the fate of their musical hero. It won the Academy Award for best documentary in 2013 — but the enigmatic Rodriguez did not attend the ceremony.

In an interview backstage, producer Simon Chinn explained why.

"He genuinely doesn't want to take the credit for this film....He's genuinely a humble man," Chinn said.

Rodriguez was "more popular than Elvis" in South Africa, Stephen "Sugar" Segerman said in 2013. The Cape Town record store owner's nickname comes from the Rodriguez song "Sugarman."

As his popularity in South Africa grew, Rodriguez continued to live in Detroit. But his fans in South Africa believed he also was famous in the United States. They heard stories that the musician had died dramatically: He'd shot himself in the head onstage in Moscow; He'd set himself aflame and burned to death before an audience someplace else; He'd died of a drug overdose, was in a mental institution, was incarcerated for murdering his girlfriend.

In 1996, Segerman and journalist Carl Bartholomew-Strydom set out to learn the truth. Their efforts led them to Detroit, where they found Rodriguez working on construction sites.

"It's rock-and-roll history now. Who would-a thought?" Rodriguez told The Associated Press a decade ago.

Rodriguez said he just "went back to work" after his music career fizzled, raising a family that includes three daughters and launching several unsuccessful campaigns for public office. He made a living through manual labor in Detroit.

Still, he never stopped playing his music.

"I felt I was ready for the world, but the world wasn't ready for me," Rodriguez said. "I feel we all have a mission - we have obligations. Those turns on the journey, different twists - life is not linear."

Rodriguez later pursued royalties he did not receive from his music being used and played in South Africa.

Some of Rodriguez songs were banned by the apartheid regime and many bootlegged copies were made on tapes and later CDs.

In 2012, "60 Minutes" correspondent Bob Simon asked Rodriguez how he felt not being noticed as a singer and songwriter for decades.

"Well, I just wasn't meant to be so lucky then, you know," he replied. "I think maybe that's it."

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