Veteran stand-up comic Joan Rivers was rushed to Mount Sinai Hospital in Manhattan on Thursday morning, after reportedly suffering complications during an outpatient surgery at a nearby doctor’s office. According to reports from TMZ, a 911 call received by the New York Fire Department around 9:30 a.m. EDT reveals that the 81-year-old star of Fashion Police had been undergoing throat surgery when she unexpectedly experienced either cardiac or respiratory arrest.

E! News states that Rivers had stopped breathing during surgery and was in critical condition when authorities arrived. Emergency medical services personnel then brought her to Mount Sinai from “a doctor’s office on 93rd Street,” NYPD Det. Kellyann Ort told The Times.

The news was later confirmed by hospital spokesman Sid Dinsay, who stated, “This morning, Joan Rivers was taken to the Mount Sinai Hospital in New York, where she is being attended to. Her family wants to thank everybody for their outpouring of love and support. We will provide an update on her condition as it becomes available.”

The New York Daily News overheard Rivers’ assistant Graham Reed saying, “She’s not conscious, but she’s stable.”

Rivers’ publicist has not yet responded to requests for comments on the comic’s health. A source close to Rivers’ family told CNN that Joan’s daughter Melissa and her grandson Cooper landed in New York Thursday night after a flight from Los Angeles. As of the source’s statement, the two were already en route from the airport to Mount Sinai Hospital.

Rivers has always been open about her health issues, and even allowed cameras to record a 2013 health scare for her and her daughter’s reality show, Joan & Melissa: Joan Knows Best. She was diagnosed with osteoporosis in 2002 after a fall down some stairs left her with several broken bones, and she later became an advocate for screenings for women.

“E!, Fashion Police and NBCUniversal continue to send thoughts and prayers to Joan, Melissa and their entire family,” the network said in a statement.