The co-founder of the classic rock band Steely Dan, Walter Becker, has died, according to a post on Becker's website. He was 67.

The cause has of death has not been disclosed and no other information is available on Becker's death, but the guitarist missed the band's July concerts as he recovered from an undisclosed illness, Rolling Stone reported.

Steely Dan band mate Donald Fagan told Billboard at the time that he expected Becker to be back on his feet again soon.

"Walter's recovering from a procedure and hopefully he'll be fine very soon," Fagan said.

Rolling Stone reported that Becker's doctor told him not to leave his home in Maui for the July performances.

1972: (L-R)  Jeff 'Skunk' Baxter, Walter Becker, David Palmer, Denny Dias, Donald Fagen and Jim Hodder of the rock band 'Steely Dan' pose for a portrait in 1972. 

Credit: Michael Ochs Archives

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Credit: Michael Ochs Archives

Becker and musician Donald Fagan founded Steely Dan in 1972.

The band, which was known for it’s jazz rock fusion, including blends of soul, R&B and pop music, had numerous hits during the 1970s, including “Reelin’ in the Years, “Hey Nineteen,” “Deacon Blues,” “Rikki Don’t Lose that Number” and many more.

Steely Dan achieved critical and commercial success before breaking up in 1981, then reunited again in 1993 and continued to tour.

Social media is reacting to Becker’s death.

Musician Walter Becker of Steely Dan performs onstage during day 1 of the 2015 Coachella Valley Music & Arts Festival (Weekend 1) at the Empire Polo Club on April 10, 2015 in Indio, California. 

Credit: Jeff Kravitz

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Credit: Jeff Kravitz