Ron Machen, the U.S. Attorney for the District of Columbia, sat down with NBC4’s Tom Sherwood for a rare public interview yesterday and finally spilled some beans on his ongoing investigation of political corruption in the city. Specifically, questions around Mayor Vince Gray’s 2010 campaign.

While Machen was mostly tight-lipped, for obvious reasons, he did give some insight as to what’s taking him so long to close the investigation, which could shed some light on if Gray knew about businessman Jeffrey E. Thompson’s alleged “shadow campaign.” With the upcoming mayoral primary in April, those seeking to declare their candidacy have little more than a month to do so. Gray, so far, has been pretty coy with reporters about his reelection status.

Machen told Sherwood that certain “challenges and obstacles” have kept him from closing out his investigation of Gray’s campaign, citing difficulty working with D.C.’s Attorney General Irvin B. Nathan to gain access to certain documents that relate to the 2011 settlement with a health-care firm that Thompson owned.

When pressed on “Thompson’s alleged role in the investigation or many other specifics,” Machen did not give in, The Post reports.

And as to what they’ve been doing for three years on this investigation? Machen said, “It’s not like we’ve been looking at this for three years and there’s no there there. I mean, there’s there there, and we’re trying to gather information, we’re trying to get documents, and we’re trying to talk to people.”

He also said, “Some of the same people who are saying ‘Hurry up, hurry up’ may also be involved in not coming forward with the information we need.”

On NewsTalk With Bruce DePuyt this morning, Gray said “I don’t know who he’s referring to or what he’s referring to.” When asked about how the investigation is influencing his decision to seek reelection, Gray, who has denied any wrongdoing, said “We’d love this situation with this investigation to be over with.”