Schitt’s Creek star Catherine O’Hara died from a pulmonary embolism, with cancer as the underlying cause.

A Los Angeles County death certificate issued on Monday (local time) lists the pulmonary embolism, which occurs when a blood clot blocks an artery in the lungs, as the immediate cause of the actor’s death on January 30 at the age of 71.

Rectal cancer was the long-term cause.

The oncologist who signed the certificate indicated that he had been treating the Canadian actress since March and last saw her on January 27.

O’Hara died at a hospital in Santa Monica, California.

The beloved Canadian-born comic actress and SCTV alum starred as Macaulay Culkin’s mother in two Home Alone movies and won an Emmy as the dramatically oblivious wealthy matriarch Moira Rose in Schitt’s Creek.

“Mama. I thought we had time,” Culkin wrote in a poignant tribute after her death.

“I wanted more. I wanted to sit in a chair next to you. I heard you but I had so much more to say. I love you. I’ll see you later.”

O’Hara was one of seven children and her first experience of acting was playing the Virgin Mary in a nativity play. After leaving school, she worked as a waitress at the Second City Theatre in Toronto, encountering the likes of Dan Aykroyd, and Joe Flaherty.

“I was lucky enough to watch everybody,” she told People in 2024.

O’Hara eventually joined the company in 1974. However, she later confessed to feeling anxious whenever she was on the stage.

“My crutch was, in improvs, when in doubt, play insane. Because you didn’t have to excuse anything that came out of your mouth. It didn’t have to make sense,” she told The New Yorker in 2019.

O’Hara eventually landed a role on a TV sketch show called Second City Television, which aired on NBC in the 80s. She became famous for her impressions of celebrities, including Meryl Streep and Brooke Shields.

Her film debut came in 1980, when she starred alongside John Candy and Eugene Levy in Double Negative.

In 1988, she starred as Delia Deetz, the stepmother of Winona Ryder’s Lydia, in the hit movie Beetlejuice, which was a huge commercial success. She revived the role for the 2024 sequel.

Last year, O’Hara starred alongside Seth Rogen in Apple TV’s The Studio, playing Patty Leigh, a former studio head and the mentor of Matt Remick, played by Rogen.

At the 78th Annual Directors Guild of America Awards on Saturday, the show’s collaborators honoured her.

“There’s no one we wish we could thank in person at this moment more than we would love to thank Catherine O’Hara,” Rogen said.

“Home Alone, honestly, is like the movie that made me want to make movies in a lot of ways.”

O’Hara’s death was a surprise to most and an initial statement from her representatives said only that she died “following a brief illness”.

Collaborators including Culkin, Christopher Guest, Eugene Levy and Pedro Pascal paid her loving tributes after her death.

The document said O’Hara was cremated.

-with AAP