CHICAGO – The longest-serving state House speaker in modern American history is a subject of inquiries in an ongoing federal corruption investigation that has already entangled several top Illinois Democrats, according to a newspaper report published Thursday. Four people interviewed by investigators told the Chicago Tribune that FBI agents and prosecutors asked about Illinois House Speaker Michael Madigan’s ties to ComEd lobbyists, contracts the utility had with Madigan associates and government jobs those close to Madigan have landed. The Tribune did not name the four people and did not offer any additional details about them, including whether they themselves were former Madigan confidants.