A BBC investigation published Tuesday claims Facebook failed to remove dozens of "sexualized" images of children on its platform — but when the news organization provided examples of the photos that had been reported to the site but not taken down by its moderators, Facebook reported the journalists to the UK's National Crime Agency.

The BBC said it used Facebook's "report" tool to alert the social network's moderators to 100 images, which were hosted inside pages explicitly for men with an interest in children, images of under 16s in "highly-sexualized poses," groups with names such as "hot xxx schoolgirls" that contained stolen images of real children, and an image that appeared to be a screenshot of a video of child abuse.

Only 18 images of the 100 were removed after the BBC reported them to Facebook. Automated replies said the other 82 did not breach Facebook's community guidelines — including the screenshot, which had included a request underneath to share "child pornography."

The BBC said it asked for an interview with Facebook's UK director of social policy, Simon Milner, to discuss its findings. Milner agreed to be interviewed only on the condition its journalists provided examples of the photos that had been reported and not removed by moderators, according to the BBC.

The BBC said it cooperated with the request but Facebook then cancelled the interview and reported the news organization to the UK's National Crime Agency.

Therein follows a complex legal and ethical debate. Under the Protection of Children Act, it is illegal in the UK to download or distribute images of child exploitation — something the BBC should have been well aware of. However, Facebook had requested the images in order for an interview to take place — and these were photos which its own moderation system had apparently deemed legal. Section 4 of the act also states one defence of distributing or being in possession of such indecent photographs is having a "legitimate reason" to do so.

Facebook says it has now removed all of the images flagged by the BBC. The social network also reported itself to the police for hosting the images.

Facebook provided Business Insider with this statement, attributed to its UK policy boss, Simon Milner:

“We have carefully reviewed the content referred to us and have now removed all items that were illegal or against our standards. This content is no longer on our platform. We take this matter extremely seriously and we continue to improve our reporting and take-down measures. Facebook has been recognized as one of the best platforms on the internet for child safety.



“It is against the law for anyone to distribute images of child exploitation. When the BBC sent us such images we followed our industry’s standard practice and reported them to CEOP (the Child Exploitation and Online Protection Center). We also reported the child exploitation images that had been shared on our own platform. This matter is now in the hands of the authorities.”

Facebook did not respond to an additional request for comment about whether the social network had solicited the images from the BBC.

The BBC's latest report follows another investigation it carried out last year, which found pedophiles were using secret Facebook groups to post and swap sexual images of children. Information from that investigation handed to police by the BBC had resulted in one man being sent to prison for four years, the BBC said.

The chair of the UK Commons media committee, Damian Collins, told the BBC he thought the latest investigation "raises the question of how can users make effective complaints to Facebook about content that is disturbing, shouldn't be on the site, and have confidence that it will be acted upon."