He wrote: "Today was greeted by the sad news of the passing of Danny Kirwan in London, England". Danny played a key-role in Mac's band during the late 1960's and early 1970's.
Kirwan leftFleetwood Mac in 1972 after a falling out with the other members of the band. Kirwan was an influence on the group's earlier blues days with co-founding guitarists Peter Green and Jeremy Spencer and contributed to their first United Kingdom #1 hit "Albatross".
The band's founding drummer, and bandmate of Kirwan, Mick Fleetwood acknowledged the guitarist's passing in a statement for the group on his personal Facebook page on Friday evening.
Thank you, Danny Kirwan. You will forever be missed!,' he added. He was aged just 18 when he joined the band, and his guitar and vocal work would go on to feature in five Fleetwood Mac albums.
But his drinking led him to be fired during the tour to promote Bare Trees. The location and cause of death was not known as of early Saturday morning.
For several years, Kirwan worked on his musical career, and he recorded three solo albums from the period between 1975 and 1979. Mick asked the Missing Person Bureau to look for Danny when he couldn't be found and in a rare interview with The Independent in 1993, Danny talked about not having a home.
Along with Fleetwood, Stevie Nicks, Lindsey Buckingham, Peter Green, John McVie, Christine McVie and Jeremy Spencer, Kirwan was inducted into the Rock and Roll Hall of Fame in 1998 for his contributions to Fleetwood Mac's formative years.
"I couldn't handle it all mentally", he said of his former stardom, "I can't settle".