Special counsel Robert Mueller has interviewed White House Chief of Staff John F. Kelly as part of his ongoing investigation into allegations of collusion between the Trump administration and Russia, according to a report Friday.

CNN reportedMr. Kelly had responded to questions from the Mueller team regarding possible obstruction of justice allegations lodged against President Trump.

Specifically, Mr. Mueller asked about relations between former White House counsel Don McGahn and Mr. Trump, who reportedly was angered by a New York Times story claiming the president tried to fire the special counsel and Mr. McGahn’s refusal to come out against the story. Mueller prosecutors wanted to corroborate Mr. McGahn’s version of events, CNN reported.

White House attorneys had rebuffed efforts by Mr. Mueller’s prosecutors to interview Mr. Kelly earlier this summer, CNN reported. The request to interview Mr. Kelly was made shortly after the raids on former Trump attorney Michael Cohen’s home and office, according to the report.

Mr. Kelly is believed to be the highest-ranking administration official to talk with the special counsel. But his interview also represents a departure from Mr. Mueller, who had largely been talking to individuals with ties to the Trump presidential campaign. Mr. Kelly did not join the White House until July 2017.

News of the Mueller interview comes amid reports that Mr. Kelly is on his way out of the Trump White House. Several outlets reported Friday that he and president are no longer on speaking terms and that Mr. Kelly is expected to resign in the coming days.