Junaid Hussain was one of the 22,000 names leaked.
Counterterrorism investigators say they are beginning to pour through a cache of documents detailing what could be the most comprehensive look into the recruiting networks luring fighters into the Islamic State group.
The IS files that surfaced late Wednesday contain names of potential fighters, names of personal references and telephone numbers.
Shiraz Maher of the International Centre for the Study of Radicalization said Friday that some of the names in the documents also appear to be of women but it was unclear whether the names could simply be of personal references. He has seen dozens of the documents.
Robert Wainwright, director of the European police organization, said Europol is sharing its own database with member states to allow them to crosscheck names of nationals who may appear in the documents.