The inquiry, which was started by Attorney General Eric H. Holder Jr. last June, is examining leaks about a computer virus developed jointly by the United States and Israel that damaged nuclear centrifuges at Iran’s primary uranium enrichment plant. The U.S. code name for the operation was Olympic Games, but the wider world knew the mysterious computer worm as Stuxnet.

Prosecutors are pursuing “everybody — at pretty high levels, too,” said one person familiar with the investigation. “There are many people who’ve been contacted from different agencies.”