Rivers, who was undergoing a procedure on her vocal cords at an Upper East Side clinic, was rushed to Mt. Sinai Hospital in "cardiac and respiratory arrest" shortly after 9:30 AM, according to FDNY.
Rivers has been upgraded from critical to stable condition, according to Deadline.com.
"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," a representative for the hospital said in a statement.
Playbill.com will continue to update.
Rivers made her Broadway stage debut in Fun City and later was a replacement player in Neil Simon's Broadway Bound. A stand-up comic making guest-host appearances on "The Tonight Show," Rivers eventually hosted her own talk show, "The Joan Rivers Show." She received a Tony Award nomination for Best Actress for her work in Sally Marr...and Her Escorts — which she also co-wrote. Her most recent theatrical outing was in her autobiographical A Work in Progress by a Life in Progress. Rivers frequently performs her stand-up act at the Laurie Beechman Theatre in midtown Manhattan.