The FBI reportedly operated almost two dozen child pornography websites hidden on the dark web to lure and catch predators.

Unsealed documents obtained by the American Civil Liberties Union revealed investigators had the authorization to run 23 such websites.

It had already been known that the agency ran the website, Playpen, to help identify users.

The FBI reportedly operated almost two dozen child pornography websites hidden on the dark web to lure and catch predators

The sites were, 'dedicated to the advertisement of child pornography, the discussion of matters pertinent to child sexual abuse', according to Ars Technica.

The agency's sites also monitored: 'methods and tactics offenders used to abuse children, as well as methods and tactics offenders used to avoid law enforcement detection while perpetuating online child sexual exploitation crimes.'

The FBI hoped to distribute malware to users of the sites so that they could be identified.

The new documents also revealed the trap sites were ran out of a government facility, and they were able to learn the identities and IP addresses of users.

The FBI sites were reportedly, 'dedicated to the advertisement of child pornography, the discussion of matters pertinent to child sexual abuse'

The new information was found in documents that were obtained by the American Civil Liberties Union

Cybercrime expert Fred Jennings told Ars Technica there is: 'no other way to read (the documents) than websites 1-23 were hosted at a government facility, with the FBI's knowledge and to the FBI's informational benefit.

'It's clever phrasing on their part.'

An FBI spokesman said he was unaware of an operation with 23 websites, according to a statement given to the website.