A sitting Cook County commissioner is now under the federal microscope as part of a sprawling federal corruption investigation into lobbyists and politicians in Illinois.

The latest elected official to face scrutiny from U.S. Attorney John Lausch’s office is Cook County Commissioner Luis Arroyo Jr., D-Chicago.

Federal prosecutors issued a subpoena earlier this year to the Illinois Department of Revenue, which processes tax returns for the state. The subpoena, obtained by WBEZ through the state’s open records law, requested that the agency release tax returns for Arroyo, his lobbying firm and his wife, Desiree.

Arroyo is the son of former Democratic State Rep. Luis Arroyo, who was first charged in 2019 for allegedly offering bribes to an unnamed Illinois state senator in exchange for supporting legislation that would benefit Arroyo’s lobbying client, a sweepstakes gaming business. He has pleaded not guilty.

Like his father, the two-term Cook County commissioner was lobbying one public body while also serving as an elected official. In 2019, Arroyo Jr. filed paperwork to lobby the Illinois legislature — while his father was a member. It’s not illegal to lobby one government body while serving as an elected official in another, but state lawmakers are considering banning the practice amid the wide-ranging federal probe into Illinois lobbying that has even ensnared Illinois’ largest utility, Commonwealth Edison.

Arroyo Jr. did not respond to requests for comment. Neither he nor his wife are charged with wrongdoing.

A spokesman for U.S. Attorney John Lausch did not comment.

The subpoena does not shed light on what interests federal prosecutors about Arroyo’s taxes. But one of his 2019 lobbying clients for his firm that was named in the subpoena, Tartak Consulting, has also drawn federal scrutiny.

Lyons-based Black Dog Corporation is a company that delivers fuel and chemicals. When federal agents raided the suburban Lyons Village Hall in 2019, they specifically sought documents related to both Black Dog and its CEO, Amit Gauri.

Gauri faces no criminal charges. In response to questions about Arroyo Jr.’s lobbying on behalf of Black Dog, a spokesman for the company and Gauri denied hiring Tartak.

“Black Dog never made any payment to or used the services of Tartak Consulting and doesn’t know why it was listed as a client of the firm,” the spokesman said.

Also named on the federal subpoena to the Illinois Department of Revenue is Arroyo Jr.’s wife, Desiree, who works for ComEd, according to a company spokesman.

Last year, ComEd admitted to a years-long bribery scheme aimed at influencing former Illinois House Speaker Michael Madigan. The feds agreed not to prosecute the utility giant if it agreed to meet certain ethical standards and pay a $200 million fine.

Tony Arnold covers Illinois politics for WBEZ. Follow him @tonyjarnold.