Fans of Whitney Houston, including many celebrities, filled up Twitter feeds Saturday night with reaction to her death.

In Atlanta, topics related to Houston were trending on the online site within hours of the superstar's death.

We've compiled some of the online reaction here:

Mariah Carey (@MariahCarey): Heartbroken and in tears over the shocking death of my friend, the incomparable Ms. Whitney Houston.

Usher Raymond IV (@UsherRaymondIV): "R.I.P Whitney Houston... A true icon of our time. Gone too soon. My heart goes out to the family in their time of distress. URIV"

Smokey Robinson (@smokey_robinson): "I've known Whitney since she was a little girl and I have always loved her. She was like family to me and I will miss her dearly."

Christina Aguilera (@TheRealXtina): "We have lost another legend. Love and prayers to Whitney's family. She will be missed."

Dolly Parton: "Mine is only one of the millions of hearts broken over the death of Whitney Houston. I will always be grateful and in awe of the wonderful performance she did on my song, and I can truly say from the bottom of my heart, ‘Whitney, I will always love you. You will be missed.'"

Justin Bieber (@justinbieber): "just heard the news. so crazy. One of the GREATEST VOICES EVER just passed. RIP Whitney Houston. My prayers go out to her friends and family

Tionne T-Boz Watkins (@TheRealTBOZ): "My heart goes out to her family. My heart is broken. She was & is special. TLC started out with her"

Rihanna (@rihanna): "No words! Just tears #DearWhitney"

Sara Evans (@saraevansmusic): "What a tragedy losing Whitney Houston. One of my all time idols. So very sad for her family. I will be praying for them.

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Simon Cowell (@SimonCowell): "I am so sad to hear about Whitney. We have lost one of the greatest singers of all time."

Toni Braxton (@tonibraxton): "She's paved the way for every single singer in the music industry. Iconic, legendary, innovating, amazing, humble...1 the best in the world"

Ciara (@ciara): "RIP Whitney Houston. A Legend lost:( Her voice was insurmountable, her smile was illuminating, she was truly one of a kind and a huge inspiration to me."

Ellen DeGeneres (@TheEllenShow): "Very sad news about Whitney. My heart and prayers go out to her daughter and family."

Alicia Keys (@aliciakeys): "I feel sick.... Life is precious, we are fragile souls. Let's love each other! I miss you beautiful Whitney, the whole world misses you!!"

Ryan Seacrest (@RyanSeacrest): "Shortly after news broke, grammy producers reached out to jennifer hudson to sing whitney tribute, she's now confirmed...plans in motion..."

Wendy Williams (@WendyWilliams): "My family & I are saddened by the loss of a true icon & legend -- Whitney Houston. Our thoughts & prayers are w/ the entire Houston family."

Cee Lo Green (@CeeLoGreen): "R.I.P. Sister WHITNEY HOUSTON!!!!! We will always love you."

William Shatner (@WilliamShatner): "My thoughts and prayers are with the family of Whitney Houston."

Forest Whitaker (@ForestWhitaker): "May gods breath surround you, Whitney. And may you be held in the arms of the angels. Please, pray to comfort all those who hold her dear"

Tony Bennett (@itstonybennett): "It's a tragedy. Whitney Houston was the greatest singer I've ever heard and she will be truly missed."