Joan Rivers is in a New York City hospital Thursday after she was rushed from a doctor's office when she went into cardiac arrest, police and hospital officials said.
The 81-year-old comedian's condition wasn't immediately known.
"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," said Sid Dinsay, a spokesman for Mount Sinai Hospital. "We will provide an update on her condition as it becomes available."
New York City police officials, who spoke on the condition of anonymity because they weren't authorized to publicly name Rivers, said she was taken to the hospital just after 9:30 a.m. Thursday.
Rivers' representatives didn't immediately respond to requests for comment.
The entertainer has logged a half-century in show business and gave rise to red carpet commentary — and the snarky criticism that often accompanies it. Her signature red carpet query: "Who are you wearing?"
She continues to maintain a busy schedule, and was to perform a show Friday at the Count Basie Theatre in Red Bank, New Jersey. That show was postponed because of her hospitalization.
Rivers spoke at an employee event at Time Inc. in New York on Wednesday night and appeared healthy, practically jogging when she walked in to take her seat, said Shira Blum, an online project manager.
"She seemed totally healthy," Blum said. "She was very energetic, hilarious, funny. And it was such a shock, a surprise to hear the news this morning."
Rivers took questions and said she wakes up every morning and "is thankful that everything works," Blum said.
The host of "Fashion Police" on E! network, Rivers also presides over an online talk show, "In Bed With Joan" and co-stars with her daughter, Melissa, on the WEtv reality show, "Joan & Melissa: Joan Knows Best?"
Her latest book, "Diary of a Mad Diva," was released this summer.
In 2009, Rivers emerged as the winner of NBC's "The Celebrity Apprentice." A documentary, "Joan Rivers: A Piece of Work," premiered in theaters in 2010.
A native of New York, Rivers originally entered show business with the dream of a theatrical career, but comedy became a way to pay the bills while she auditioned for acting roles.
"Somebody said, 'You can make six dollars standing up in a club,'" she told The Associated Press in 2013, "and I said, 'Here I go!' It was better than typing all day."
After proving herself in comedy clubs as a rarity — a woman comedian — Rivers was a smash on her first booking on "The Tonight Show Starring Johnny Carson" in 1965. "God, you're funny," Carson told her.