BERLIN — Germany’s federal criminal police said Thursday they are in possession of files containing personal data on members of the extremist Islamic State group and believe them to be authentic.

The announcement came after Britain’s Sky News reported it had obtained 22,000 Islamic State files on the border with Turkey and Syria, files that detail IS fighters’ real names, where they were from, telephone numbers, and even names of those who sponsored and recruited the militants.

Though the significance of these files is yet to be gauged, they could be the largest yet treasure trove of documents found on IS and the most significant leak on its past and present fighters and operations across the Mideast.

They could also shape the campaign against the extremist group, which emerged from al-Qaida in Iraq. The cache, exposing its members and their families, could undermine its future ability to recruit and inspire would-be members.

US Army Col. Steve Warren, spokesman for the U.S.-led coalition against the Islamic State, said the information could help the coalition fight the Islamic State group by aiding in a crack-down on IS’s foreign fighter networks.

He said that while he was not able to verify the documents, he hoped that “if there is a media outlet that has these names and numbers, I hope they publish them.” This would help bring attention to the problem of foreign fighters joining IS, and would help law enforcement crack down on the problem, he said.

“This would allow the law enforcement apparatus across the world to become much more engaged and begin to help do what we can to stem this flow of foreign fighters — so we’re hopeful that its accurate and if so we certainly plan to do everything we can to help,” he said.

Sky said the files were passed on to them on a memory stick stolen from the head of Islamic State’s internal security police by a former fighter who had grown disillusioned with the group.

Germany’s Sueddeutsche Zeitung newspaper reported it had also obtained “dozens” of similar files on the Turkey-Syria border, where it said Islamic State files and videos were widely available from anti-IS Kurdish fighters and also members of the Islamic State group itself.

Both Sky and the Sueddeutsche reported that the documents were forms with 23 questions filled out by recruits when they were inducted into the Islamic State. Sky said they included nationals from at least 51 countries.