U.S. prosecutors are investigating an international network of traders suspected of infiltrating banks and companies to glean confidential information on mega-deals, according to people familiar with the matter.

The probe by prosecutors at the U.S. Attorney’s Office for the Southern District of New York is focusing on a group of stock pickers in Europe and the Middle East who have made tens of millions of dollars trading ahead of media reports about takeover talks or merger announcements by companies, according to the people, who asked not to be identified because the matter isn’t public. The investigation is part of a years-long multinational effort, with U.S., U.K., and French prosecutors operating on parallel tracks.