Former White House chief of staff Reince Priebus has submitted to questioning by investigators looking into Russian interference in the US presidential campaign.
US media are reporting that Mr Priebus was questioned in the probe into possible collusion by associates of President Donald Trump.
Politico and the Washington Post quoted Mr Priebus's lawyer William Burck as saying the interview with members of Special Counsel Robert Mueller's team was voluntary.
"He was happy to answer all of their questions," Mr Burck said.
Mr Priebus himself did not comment but Politico said he had been preparing for several weeks for the interview.
Mr Trump has not been accused of any wrongdoing, but Mr Mueller's team has shown interest in the president's firing of former FBI director James Comey over his Russia probe, according to the reports.
Other areas of interest are reportedly Mr Trump's eldest son's meeting with a Kremlin-linked lawyer during the campaign and Mr Trump's meetings at the White House with Russian officials.
Mr Priebus participated in meetings where Mr Comey's firing was discussed, and played a key role in the White House as well as during the campaign as head of the Republican National Committee.