Prosecutors and FBI agents investigating Hillary Clinton’s use of a personal email server have so far found scant evidence that the leading Democratic presidential candidate intended to break classification rules, though they are still probing the case aggressively with an eye on interviewing Clinton herself, according to U.S. officials familiar with the matter.

FBI agents on the case have been joined by federal prosecutors from the same office that successfully prosecuted 9/11 conspirator Zacarias Moussaoui — and who would handle any Edward Snowden case, should he ever return to the country, according to the U.S. officials familiar with the matter. And in recent weeks, prosecutors from the U.S. Attorney’s Office in the Eastern District of Virginia and their FBI counterparts have been interviewing top Clinton aides as they seek to bring the case to a close.