Joan Rivers' Family Keeping 'Our Fingers Crossed' for Iconic Comedian

Rivers has been sedated and under close supervision for three days.

"Thank you for your continued love and support," Melissa Rivers said in a statement today. "We are keeping our fingers crossed."

Her mother arrived at Mount Sinai Hospital Thursday after an emergency call that she was in cardiac arrest at an Upper East Side clinic, Yorkville Endoscopy, sources said.

Doctors are intentionally keeping her sedated and under close supervision until they're more comfortable with her condition, which remains "serious."

Reaction has been widespread, including overwhelming online support from the likes of Donald Trump, Montel Williams and Kelly Ripa.

WATCH: Melissa Rushes to Be by Joan Rivers' Side

Read: Joan Rivers 'Resting Comfortably' in Hospital

Here are some of those messages.