WASHINGTON (AP) — Rudy Giuliani, who as a member of Donald Trump's legal team sought to overturn 2020 presidential election results in battleground states, was interviewed recently by investigators with the Justice Department special counsel's office, according to a person familiar with the matter.

The interview was conducted voluntarily and was not done before a grand jury, said the person, who insisted on anonymity to discuss an ongoing investigation. The person would not say what questions investigators asked.

The interview is an additional sign of busy investigative activity by special counsel Jack Smith as his team of prosecutors scrutinizes efforts by Trump and his allies to undo the results of the election in the weeks before the Jan. 6, 2021, riot at the Capitol.

Smith filed a separate case earlier this month charging Trump with illegally retaining classified documents at his Florida home, Mar-a-Lago.

As a lawyer for Trump, Giuliani pushed bogus legal challenges to the presidential election results. The legal team filed lawsuits in battleground states raising unsupported claims of vast election fraud even though officials, including Trump's own attorney general, William Barr, said no such pervasive problems existed.

Giuliani's efforts have made him a key figure in investigations. He was interviewed last year by a House committee that investigated the run-up to the Jan. 6 attack and by prosecutors in Fulton County, Georgia, who have been investigating efforts to subvert that state's election.

Justice Department prosecutors have for months now been examining what role Trump legal advisers played in working to undo the election. Last July, John Eastman, a conservative lawyer who aided Trump's efforts to challenge the election results, reported that federal agents had seized his phone.

A spokesman for the special counsel's office did not immediately return an email seeking comment.

CNN first reported the interview with Giuliani.