Germany's federal criminal police said Thursday that they were in possession of files containing personal data on members of the extremist group Islamic State of Iraq and Syria (ISIS) and believed them to be authentic.
Thursday's announcement came after Britain's Sky News reported it had obtained 22,000 ISIS files on the border with Turkey and Syria, handed over, the network said, by a disgruntled former ISIS figure, detailing members' real names, telephone numbers, and even names of those who sponsored and recruited the fighters.
Germany's Sueddeutsche Zeitung newspaper reported it had also obtained "dozens" of similar files on the Turkey-Syria border.
A spokeswoman for the Bundeskriminalamt said her agency was evaluating the files. She spoke on condition of anonymity to discuss the matter. She declined to say where the agency obtained the files, how many documents were involved or how long it had had them.
U.S. intelligence officials are also looking into the documents and evaluating their authenticity, CBS News learned Thursday.
CBS News consultant Richard Walton, former head of counterterrorism for the London Metropolitan Police, said that if the documents are authentic, it would be one of the most significant intelligence finds since ISIS was created.
However, Syrian opposition media group Zaman Al Wasl has published dozens of purported ISIS recruitment forms over the past two days, seemingly representing the same batch of documents that found their way into the hands of the German government and Sky News.
Zaman Al Wasl said in a statement Wednesday that it had obtained 22,000 documents near the end of 2015, but that many of them were duplicates. In total the opposition group said it had ISIS application forms for about 1,736 individual recruits.
The opposition group published 144 of the documents online Wednesday and Thursday.
CBS News cannot independently verify their authenticity, or whether it is positively from the same collection of digitized forms that Germany obtained. Zaman Al Wasl also did not reveal how it had obtained the documents.
The smaller number of unique documents, and the fact that all the forms appear to date from 2014, could mean slightly less intelligence value to Western governments than first hoped, but it would still be an impressive trove.
Each form has 23 spaces, requesting information including names, aliases, dates of birth, marital status, education, profession, countries of residence, countries travelled through to reach ISIS territory, phone numbers, etc.
In one of the fields, applicants are asked to choose a position to apply for, and the opposition group said 122 out of the 1,736 recruits selected "martyrdom seeker," or suicide bomber.
Zaman Al Wasl said Arabs made up more than 72 percent of the recruits, based on a representative sample of the application forms, with Saudis being the largest share at 27 percent. Tunisians accounted for 21 percent. Among the non-Arab recruits, there were application forms from 35 Frenchmen, 18 Germans, 16 Britons, six Canadians and four Americans.
The Combating Terrorism Center at West Point has said there are likely about a dozen U.S. nationals fighting for Islamic extremist groups in Syria and Iraq.