By Miles Raymer
Updated July 17, 2014 at 03:35 PM EDT
Michael Putland/Getty Images

Guitarist Johnny Winter, one of the leading figures in the electric blues movement of the '60s and '70s, was found dead at age 70 on Wednesday in a hotel room in Zurich, Switzerland. The cause of death is unclear, but while a prosecutor has ordered an autopsy, early evidence indicates a medical cause, Reuters reports.

Winter's best known record, "Rock and Roll, Hoochie Koo," written by his former bandmate Rick Derringer, remains one of the definitive songs from the classic rock era, but Winter considered himself a blues musician rather than a rocker. Over the course of his career, he played alongside some of the style's most respected figures, including Willie Dixon, B.B. King, Sonny Terry, James Cotton, and Muddy Waters (for whom he produced three studio albums and one live album), and along with Eric Clapton and Mike Bloomfield he helped to bring traditional blues techniques in the acid-rock era. He was inducted into the Blues Foundation's Blues Hall of Fame in 2003.

Winter remained productive into his later years. A sequel to Winter's 2011 album Roots, entitled Roots 2,is scheduled to be released on September 2, and will feature contributions by Clapton, Ben Harper, and Billy Gibbons of ZZ Top. Earlier this year Sony Legacy released a four-disc retrospective of Winter's career, True to the Blues, and at this year's South by Southwest festival he debuted a documentary on his life, Johnny Winter: Down and Dirty, directed by Greg Olliver, that deals with his long-running struggle with opiate addiction.