New York (CNN Business) Friday was a bad day for private prisons.

Democratic presidential candidate Elizabeth Warren is calling for private correctional and detention facilities to be banned. Shares of private prison operators dropped following her remarks.

CoreCivic's CXW The GEO Group GEO Private prison operatorstock was down 5%. Shares of, a Florida-based private prison and detention company, fell 5.6%. The broader stock market was flat to slightly higher on Friday.

Warren's campaign said it was unfazed by the stocks' slump.

"They shouldn't have a share price because they shouldn't exist," said Kristen Orthman, spokeswoman and director of communications for the Warren campaign.

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