Catherine O'Hara died from a pulmonary embolism, according to the actress's death certificate, which was obtained by USA TODAY on Feb. 9. TMZ was first to report the news.
A pulmonary embolism is a blood clot that blocks blood flow to an artery in the lung, according to the Mayo Clinic.
This is considered a medical emergency as it causes issues with blood flow and oxygen levels in your lungs, the Cleveland Clinic adds.
According to reports, O'Hara, 71, died within hours of the onset of symptoms, the document reads. She was also diagnosed with rectal cancer, according to the death certificate.
Here's what to know about the health complication.
