Paramount is investigating claims Sylvester Stallone mocked extras on the set of "Tulsa King," a source close to the show confirmed to Fox News Digital.

The comedy-drama series is facing allegations of a "toxic environment," which reportedly led to the resignation of casting director Rose Locke. 

While filming season 2 of the Paramount series, Stallone and director Craig Zisk both allegedly made disparaging remarks about the physical appearance of background actors.

Paramount "recently" became aware of a social media post floating around the internet, and prides itself on maintaining a "fair and respectful workplace," the show insider told Fox News Digital.

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Sylvester Stallone on the red carpet

Sylvester Stallone has been accused of mocking the appearance of background actors on "Tulsa King." (Getty Images)

The allegations that Stallone mocked extras on the set of "Tulsa King" were first brought to light on X, formerly Twitter, by Julie Benson. The "Star Trek: Prodigy" writer has since deleted her post.

"Got this disturbing news from my Atlanta friend who’s background on Tulsa King this wk," she wrote, according to Variety. "Casting agent quit because she was so disgusted. My friend is feeling anxious about working now. @TheSlyStallone what do you have to say for yourself, sir? Beyond disappointed, I’m livid."

The post included a screenshot of a Facebook post with the username blurred out.

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Actor Sylvester Stallone poses at the Los Angeles County Museum of Art (LACMA) Art+Film Gala in Los Angeles, October 29, 2016. REUTERS/Danny Moloshok - S1BEUJWRPXAA

Sylvester Stallone plays the lead character in "Tulsa King." (Reuters)

Stallone allegedly said, "What the F--- is happening with these F---ing ugly background," according to the screenshot.

The anonymous Facebook post added: "He and the director proceeded to call certain people terrible names and laughed at them." And then, "Sly said, ‘Bring in pretty young girls to be around me.'"

Neither representatives for Stallone nor Zisk responded to Fox News Digital's request for comment.

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Craig Zisk at the Emmys

Craig Zisk was mentioned in the allegations against Sylvester Stallone. Zisk is the director of "Tulsa King." (Getty Images)

The post also included a screenshot of an email from Locke in which she said, "At the end of the day I resigned because it was a clear toxic environment that I was not comfortable putting myself or background artists in."

The casting director also shared her phone number with the recipients of the email, encouraging them to share anything they "saw or heard" on set.

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"I will be sending the info to HR," her email concluded.

Locke did not respond to Fox News Digital's request for comment.