Christine McVie died from a stroke, her death certificate has shown.
The Fleetwood Mac singer-songwriter died in November last year at the age of 79, following what was described as a "short illness".
Alongside an "ischemic stroke" on her death certificate, which was obtained by US media, "atrial fibrillation" and "large atrial thrombus" are also listed as primary factors in her death.
Ischemic strokes are the most common form of strokes, according to the NHS, and happen when "a blood clot blocks the flow of blood and oxygen to the brain".
Atrial fibrillation causes an irregular and abnormally fast heart rate, while atrial thrombus is a form of blood clot.
Also listed on McVie's death certificate as a secondary cause is a "metastatic malignancy of unknown origin", which is a cancer that spreads throughout the body.
McVie was a later addition to Fleetwood Mac, which is one of the most successful bands in music history, joining Mick Fleetwood, Stevie Nicks, Lindsey Buckingham, and her husband John McVie.
Among the tracks she penned was Little Lies, one of the group's biggest hits, as well as Make Loving Fun, Oh Daddy and Blackbird.
She also co-wrote the four songs on Rumours, as well as the album's The Chain, which had a second life as the theme to the Formula One BBC TV coverage from the late 1970s, on and off until the 2015.
Many of the songs on Rumours documented the break-up of McVie and her husband John McVie - along with the split of fellow singer/songwriters Stevie Nicks and Lindsey Buckingham, adding to the album's notoriety.
McVie was among the eight members of the band who were inducted into the Rock & Roll Hall of Fame in 1998, and she left the band a short time later following the death of her father.
She had a successful solo career and reunited with her bandmates in 2013 after a 15-year hiatus.
In 2017, she revealed that she had retreated from the world and developed agoraphobia after leaving Fleetwood Mac and moving from California to Kent.