I don't see it prudent to submit to an interview even when the agents assure you that the interview is only administrative or that they are not investigating you. The agent can lie without penalty. Unless this is something official, in writing, from the AUSA's office that was verified by one's lawyer, it's likely to be a trick. It's a standard tool in any law enforcement officer's arsenal. I always see scenes on TV where in an emergency people talk to the FBI telling them where the perp went or some other details and I think: if this were real life, I would expect the FBI to be turned away every time, even when lives are at risk and people will die because the FBI cannot get the information they need. It's too bad that this is the kind of society we chose to create, one where trying to help law enforcement is simply too risky to oneself.