Catherine O'Hara's cause of death — and a private battle with cancer — has come to light weeks after the "Schitt's Creek" and "Home Alone" star died at 71.

The Los Angeles Medical Examiner's Office determined that the beloved comedian died of a pulmonary embolism, a blood clot in the lungs, according to her death certificate published Monday by TMZ. The document also revealed that O'Hara battled rectal cancer, which was listed as an underlying condition.

Emmy winner O'Hara, also known for "Best in Show," "Beetlejuice" and recently "The Last of Us" and "The Studio," died Jan. 30. Her agency CAA confirmed at the time that the actor, celebrated for her portrayal of narcissistic former soap star Moira Rose in "Schitt's Creek," died after a brief illness. The agency did not provide additional information at the time.

News of O'Hara's death quickly sparked tributes from her co-stars and peers, including her "Home Alone" son Macaulay Culkin and longtime collaborator Eugene Levy. Culkin penned a moving tribute to O'Hara and posted photos of them sharing an embrace in their 1990 holiday hit and a 2023 reunion at the ceremony for Culkin's star on the Hollywood Walk of Fame. "Mama. I thought we had time," the actor said.

Levy said he cherished his time working with O'hara and their years of friendship. His son, Dan Levy, who co-created and starred in "Schitt's Creek," said his TV mom was extended family.

"It's hard to imagine a world without her in it. I will cherish every funny memory I was fortunate enough to make with her," he wrote on Instagram.

Other stars who paid tribute to O'Hara include her TV daughter Annie Murphy, "The Studio" co-star Seth Rogen, Michael Keaton and Justin Theroux. Filmmakers Chris Columbus, Tim Burton and Martin Scorsese also saluted the late star.

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—Staff writers Tracy Brown and Malia Mendez contributed to this report.

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