Federal investigators have quizzed former Donald Trump lawyer Rudy Giuliani as part of their investigation into the 45th president’s efforts to overturn the 2020 election.

The former New York City mayor was joined by his attorney Robert Costello for the recent interview, though it is not entirely clear which topics were broached during the questioning, CNN reported late Tuesday.

“The appearance was entirely voluntary and conducted in a professional manner,” Giuliani adviser Ted Goodman told the outlet.

Special counsel Jack Smith was tasked last year with overseeing the Justice Department’s two investigations revolving around the 77-year-old Trump: his role in contesting the 2020 election and the subsequent Capitol riot on Jan. 6, 2021, as well as the retention of classified documents at his Mar-a-Lago resort.

Investigators have brought multiple witnesses before a federal grand jury in the election probe over recent weeks and have doled out numerous subpoenas.

At least five Secret Service agents have testified, according to multiple recent reports, while former Vice President Mike Pence appeared before the panel in April.

As Trump’s lawyer, Giuliani was a key figure in efforts by the former president’s allies to mount legal challenges to the 2020 election, most notably by furnishing slates of fake electors in multiple key states in a bid to tip the election away from Joe Biden.

Prosecutors have sought communications involving Giuliani and other members of Trump’s outside legal team, including Sidney Powell and John Eastman, as well as Justice Department official Jeffrey Clark.

Giuliani’s election activities have also put him into the crosshairs of Fulton County, Ga. investigators examining whether Trump world breached state law in their election endeavors.

The former mayor testified this past August in the Fulton County inquiry, which exhibited an interest in Giuliani’s testimony before Georgia state lawmakers in December 2020 — during which he peddled dubious claims about voter fraud.

Fulton County district attorney Fani Willis is currently mulling potential charges in that probe, including against the former president.

Reps for Giuliani and the Justice Department did not immediately respond to requests for comment.