Christine McVie died of an “ischemic stroke” in November, according to a report citing her death certificate.

The British vocalist and keyboardist, who was best known for bringing her talents to Fleetwood Mac, died on Nov. 30 at a hospital after a “short illness.” She was 79.

The certificate, obtained by the Blast on Monday, listed the stroke as the primary cause of death. According to the Mayo Clinic, an ischemic stroke “occurs when the blood supply to part of the brain is interrupted or reduced, preventing brain tissue from getting oxygen and nutrients.”

The secondary cause of death listed on the certificate was “metastatic malignancy of unknown primary origin.” According to the Blast, “Cancer had spread in her body where the primary source or tumor is not detected.”

McVie, according to her death certificate, also had “atrial fibrillation” (a common type of irregular heartbeat) and “large atrial thrombus.”

At the time of her death, McVie’s family said she “passed away peacefully” but did not reveal additional details. Months before, in June, the singer told Rolling Stone that she was in “quite bad health,” describing a chronic back problem that made it difficult for her to stand.

“There are no words to describe our sadness at the passing of Christine McVie,” Fleetwood Mac said in a joint statement following her death.

“She was truly one-of-a-kind, special and talented beyond measure. She was the best musician anyone could have in their band and the best friend anyone could have in their life. We were so lucky to have a life with her. Individually and together, we cherished Christine deeply and are thankful for the amazing memories we have. She will be so very missed.”

Drummer Mick Fleetwood and singer Stevie Nicks paid tribute to their late collaborator with separate Instagram posts. In a handwritten letter shared on social media, Nicks mourned her “best friend in the whole world.”

“Since Saturday, one song has been swirling around in my head over and over and over. I thought I might possibly get to sing it to her, and so, I’m singing it to her now,” she wrote. “I always knew I would need these words one day (written by the Ladies Haim).”

Nicks then shared lyrics to Haim’s “Hallelujah.”

“I had a best friend / But she has come to pass / One I wish I could see now / You always remind me / That memories will last / These arms reach out / You were there to protect me / Like a shield / Long hair running with me / Through the field / Everywhere / You’ve been with me all along,” Nicks wrote.