Rodriguez, the singer-songwriter whose unlikely career was the subject of Oscar-winning documentary Searching for Sugar Man, has died at 81.

The news was announced on his official site with his cause of death unknown. “It is with great sadness that we at Sugarman.org announce that Sixto Diaz Rodriguez has passed away earlier today,” the official statement read. “We extend our most heartfelt condolences to his daughters – Sandra, Eva and Regan – and to all his family. Rodriguez was 81 years old. May His Dear Soul Rest In Peace.”

The Michigan-born musician had struggled to sell many copies of his first two albums in the US in the 1970s and so quit to take on manual work. But his music gained popularity elsewhere in places such as Botswana, South Africa, Australia and New Zealand.

His cult popularity in Australia led to a 1979 tour of the continent while in South Africa, a compilation album went platinum as a rumour started that he had killed himself.

It wasn’t until 1997 that he discovered his fame in South Africa after his daughter found information online. He then went on tour in the country. Further fame followed when his song Sugar Man was covered by Paolo Nutini and South African band Just Jinger. The original song was also sampled by Nas.

His life became the subject of the 2012 documentary Searching for Sugar Man, which premiered at the Sundance film festival to acclaim. It won the Oscar for best documentary in the following year.

Directed by Swedish film-maker Malik Bendjelloul, it charts his life and the search for him. After its success, Rodriguez’s albums entered the US charts for the first time.

“It’s been a great odyssey,” Rodriguez said in a 2008 interview with the Detroit News. “All those years, you know, I always considered myself a musician. But, reality happened.”