The singer was sent home last night after falling into the bottom three alongside Stefano Langone and Jacob Lusk following this week's Rock and Roll Hall of Fame performances. She had chosen to sing Tina Turner's uptempo 'River Deep, Mountain High'.
Former contestant Hudson took to her Twitter account to say: "I can not believe they just eliminated Pia ! Really..???? ... Long as she walked away with that voice she will be alright !! Just hate to see talent like that go! (sic)."
Fellow show alumn David Archuleta wrote: "Man heard who got voted off of Idol tonight. That is pretty shocking."
Tom Hanks also shared his disappointment with followers, saying: "Don't have an IDOL habit, but how could the USA vote Pia off? I may be done for the season! HANX."
Ashton Kutcher said: "Who are the people that vote on American Idol? That's just crazy! That Pia girl is dope! #almostcriminal."
Other stars who took to the social networking site following the live show included Jersey Shore star Snooki, who wrote: "American Idol... WTF... Pia should have won the whole thing! I'm not watching Idol anymore. I'm with JLo on this one."
Alyssa Milano said: "What in the world? Pia? Pia was sent home? How is that possible? I'm so confused... Pia, keep your head up, beauty girl. You're an awesome talent", while Minka Kelly wrote: "Will someone please explain to me HOW in the WORLD @PToscanoAI10 (Pia) has been voted off American Idol?! #baffled!!"
Meanwhile, actor Dax Shepard added: "This did not just happen!!! How??? I'm going to do something radical. I love you Pia!"
Toscano took to her Twitter account after the results show to thank her famous fans for their support. "I'm truly going to miss my Idol family!" she added. "Thank you @JLo Randy and Steven for believing in me. Love you and love my fans!"
The judges voiced their disappointment at the result during yesterday's live show, and host Ryan Seacrest later told followers on his Twitter account that the audience remained seated after the show went off air because "everyone was in shock".
He added: "If u don't agree w/ the results on @AmericanIdol tonight, I remind u guys, U HAVE TO VOTE."
Toscano's departure means that just eight singers remain in the running to be crowned the winner of season ten. Next week's show will see them performing memorable tracks from the movies, while Kelly Clarkson, Jason Aldean and Rihanna will take to the stage during the results show.
American Idol airs Wednesdays and Thursdays on Fox.