Is Obama Mentor Emil Jones Under Investigation?

The Chicago Sun-Times reports that Emil Jones is stepping down.We wonder if he's being investigated? There's no evidence he is but,here's the Sun-Times:

The timing of Jones' announcement comes as a surprise, given that as Barack Obama's political godfather in Illinois, he is planning on a high-profile role within the state's delegation at next week's Democratic convention in Denver.

Jones, a former city sewer inspector, endured criticism for taking tens of thousands of dollars in interest-free loans from his campaign fund and for multimillion-dollar, no-bid government contracts steered to a technology firm headed by his stepson, John Sterling.

Why would Jones retire just as Obama is going into the Presidential spotlight?