(CNN) Celebrities are rallying behind actress Gabrielle Union and slamming NBC after her controversial exit from "America's Got Talent."

Union and fellow judge Julianne Hough will not return for the second season of "America's Got Talent: The Champions," which premieres January 6.

CNN has not independently confirmed these allegations and has reached out to reps for Union and "America's Got Talent" for comment.

Here's what other celebrities are saying about her exit:

Ellen Pompeo

The "Grey's Anatomy" star blasted the network in a series of tweets.

"Workplace cultures will continue to be toxic until there is unity and solidarity among all women. If you go for self in these moments you undermine the work we are out here trying to do. Obviously this network feels like they can operate like this and it's okay," she said. "... I support @itsgabrielleu commitment to speaking up to injustice. It takes courage."

Ellen Pompeo

Debra Messing

The "Will & Grace" star echoed Pompeo's sentiment.

"Thank you for this @EllenPompeo. This is disgusting behavior from a network that has been my professional home for decades," Messing tweeted. "Yes, women become 'difficult,' when their insistence on a respectful and professional working environment, is ignored. Addressing a hostile work environment is inconvenient when there is a huge money making machine that is involved."

Jameela Jamil

The actress, who stars on NBC's "The Good Place," said the show should bring Union back with a raise.

"I am lucky to work with really good people at @nbc and am sad and angry to know this has been going on in that same network. I stand with @itsgabrielleu," she said.

Actress Jameela Jamil

Ariana Grande

The singer's message was short and ended with a love heart emoji aimed at Union.

"Thank you for this @EllenPompeo. be better @nbc we're with you @itsgabrielleu," she said.

Singer Ariana Grande

Julian Castro

The 2020 presidential hopeful also chimed in.

"Corporate America tells employees and consumers they take racism and sexism seriously. But often the person reporting the problem is hurt by management," Castro tweeted . "Kudos to @itsgabrielleu for having the courage to speak out. Still waiting for answers from @nbc."

Julian Castro

Dwyane Wade

Union's husband said he still has questions about her exit from the show.

"... When i got the news that my wife was being fired — my first question was obviously why!? I am still waiting on a good answer to that question. But if anyone knows @itsgabrielleu or have heard of her you know she's an advocate for our community and culture. As proud as i were of her being selected as a judge on #AGT— I am even more proud of her standing up for what she stands for and that's US."

Dwyane Wade

Other celebrities, including actor Lin-Manuel Miranda, also expressed their support.

Union thanked fans on social media -- but did not provide any details on her exit from the show.

"So many tears, so much gratitude," she wrote Thursday. "THANK YOU! Just when you feel lost, adrift, alone ... you got me up off the ground. Humbled and thankful, forever."

In a statement to People, a spokesperson for NBC and Fremantle said the network and the producers take any issues on set seriously.

"America's Got Talent has a long history of inclusivity and diversity in both our talent and the acts championed by the show. The judging and host line-up has been regularly refreshed over the years and that is one of the reasons for AGT's enduring popularity," it said.