Adult video website is facing allegations of having videos depict child abuse and nonconsensual violence. Mastercard Inc., which is tied to Pornhub's privately held parent company MindGeek, said Sunday that it would investigate the allegations.

Pornhub denies it has child abuse videos on its site. “Any assertion that we allow CSAM (child sexual abuse material) is irresponsible and flagrantly untrue,” it said in a statement emailed to Reuters.

The allegations come from New York Times columnist Nicholas Kristof, whose 3,700-word column on Friday noted that videos on Pornhub contained unconscious women and girls who were being assaulted.

"The issue is not pornography but rape. Let's agree that promoting assaults on children or on anyone without consent is unconscionable," the column reads.

Kristof wrote that Pornhub doesn’t filter its content, which includes material that might contain violence or any form of assault. He also called out banks and credit card companies that work with Pornhub.

"...I don’t see why search engines, banks or credit card companies should bolster a company that monetizes sexual assaults on children or unconscious women. If PayPal can suspend cooperation with Pornhub, so can American Express, Mastercard and Visa," Kristof noted in the column.

In the summer, Pornhub faced allegations of having sex trafficking videos. There was even a petition to shut down the site.

“We are investigating the allegations raised in the New York Times and are working with MindGeek’s bank to understand this situation, in addition to the other steps they have already taken. If the claims are substantiated, we will take immediate action,” Mastercard told CNN Business in a statement. “When we identify illegal activity, our policy is to ask the acquirer to terminate the relationship, unless an effective compliance plan is put in place.”

Pornhub denied such videos exist on the site and noted that a team reviews every video.

Mastercard and Visa have been advised by billionaire investor Bill Ackman to withhold payments to the site.

Along with Pornhub, Montreal-based MindGeek also owns and operates several other popular pornography sites.

Pornhub is among three adult websites being sued by a deaf man who wants them to offer closed captions
Pornhub is among three adult websites being sued by a deaf man who wants them to offer closed captions GETTY IMAGES / Ethan Miller