Exelon Utilities CEO Anne Pramaggiore abruptly retired Tuesday amid a wide-ranging federal investigation that includes the company’s lobbying activities at the Illinois State Capitol.

The announcement of Pramaggiore’s retirement came less than a week after Exelon and its Commonwealth Edison division acknowledged they had received a second subpoena in the probe. Authorities were looking for “communications” between the companies and Illinois State Sen. Martin Sandoval, a Chicago Democrat whose home and offices were raided by FBI agents last month.

Exelon utilities include those operating in Philadelphia, Atlantic City, and Wilmington. Last month, Exelon closed Three Mile Island Unit 1 after failing to receive state financial aid.

In addition, the Illinois Senate was served with a search warrant late last month. The lengthy list of things authorities searched for included “items related to ComEd, Exelon, any employee, officer or representative of any of those businesses, Exelon Official A, Exelon Official B, Exelon Official C, Exelon Official D, and/or any issue supported by any of those businesses or individuals, including, but not limited to, rate increases.”

A source with knowledge of the investigation told the Tribune that Pramaggiore is one focus of the ongoing federal probe.

On Tuesday, Pramaggiore declined an interview request through a spokesman at a crisis communications firm. ComEd spokeswoman Jean Medina said she could not comment about Pramaggiore’s retirement beyond what was in a news release.

That statement, attributed to Exelon president Christopher M. Crane, thanked Pramaggiore “for her valuable service to Exelon and ComEd and the important contributions she made to enhance our utility operations throughout her tenure.”

In last week’s filing with regulatory authorities, the companies said they have “cooperated fully” with prosecutors’ requests. To avoid potential conflicts of interest, Exelon has formed a special oversight committee “comprising solely independent directors and advised by independent outside legal counsel” to handle the matter, the statement said.

In June, ComEd first disclosed that the company and Exelon had received a federal grand jury subpoena “requiring production of information concerning their lobbying activities” in Illinois.

The ComEd lobbying investigation dates to at least mid-May, when the FBI executed search warrants at the homes of former lobbyist Mike McClain of Quincy, a longtime confidant of Illinois House Speaker Michael Madigan; and former Chicago 23rd Ward Alderman Michael Zalewski.

The information sought by the FBI included records of communications among Madigan, McClain and Zalewski about attempts to get ComEd lobbying work for Zalewski, the Tribune has reported.

In July, the Tribune reported that federal investigators are looking into $10,000 in checks written by current and former ComEd lobbyists to Kevin Quinn, a veteran political operative who was ousted from Madigan’s organization last year over sexual harassment allegations against a campaign worker. He’s the brother of 13th Ward Alderman Marty Quinn.

Pramaggiore, who also was senior executive vice president, was a key player in ComEd’s success over the years in Springfield. Exelon and ComEd employ one of the largest lobbying contingents at the Capitol and historically are among the biggest campaign contributors to state lawmakers. Pramaggiore oversaw all six Exelon utilities throughout the U.S., including ComEd.

Pramaggiore previously served as president and chief executive of ComEd before moving into the bigger role with the Exelon parent company.

Named as interim CEO of Exelon was Calvin G. Butler Jr., the CEO of Baltimore Gas and Electric Co.

Both in her roles at ComEd and Exelon, Pramaggiore consistently has been a prolific donor to Illinois politicians, giving more than $240,000 dating to 2005.

State campaign finance records show Pramaggiore gave money to some of the state’s top Democrats, including $16,500 to funds controlled by embattled Alderman Edward Burke and $20,250 to Cook County Board President Toni Preckwinkle.

Pramaggiore also gave $10,000 to the campaign of former Mayor Rahm Emanuel, who invited Pramaggiore and her husband, Michael Harrington, on a junket to Rome for the elevation of then-Chicago Archbishop Blase Cupich to cardinal. At the time, employees of ComEd and Exelon had made more than $183,000 in contributions supporting Emanuel, the Tribune has reported.