According to TMZ, the 81-year-old comic was having surgery at an undisclosed clinic on the Upper East Side when her heart stopped beating. "We have somebody in either cardiac or respiratory arrest," a caller told 911 operators.
According to reports, the Fashion Police host is believed to be in critical condition and her daughter, Melissa Rivers, is en route to New York.
Rivers has been a show business mainstay for 60 years. She first rose to prominence as a frequent guest on The Tonight Show Starring Johnny Carson. She would later use her trademark raspy voice and acerbic wit to poke fun at Hollywood's ingenues as a fashion critic and red carpet staple on the E! network.
We'll have more on this story is as it develops. (TMZ)
Update: Joan Rivers' condition has been upgraded to stable.