Former Trump campaign foreign policy adviser Carter Page has appeared before a grand jury working with special counsel Robert Mueller, the New York Times reported Friday.

“Page was questioned by the FBI earlier this year and has also appeared before the grand jury as part of the special counsel’s inquiry,” the Times noted, in a report on Page acknowledging that he met with a senior Russian government official during a trip to Russia in July 2016.

Mueller’s team has kept a tight lid on leaks, and news of individuals’ appearances before a grand jury being used for his investigation is rare. The Times did not specify when Page appeared before the grand jury.

Paul Manafort’s spokesperson testified before Muller’s grand jury roughly six weeks before the a 12-count indictment against him and his deputy, Rick Gates, was unsealed.

Manafort’s real estate agent, Wayne Holland, confirmed to Politico, in a report published Oct. 27, that he had appeared before Mueller’s grand jury the previous week. On Oct. 30, CNN first reported that Mueller’s grand jury had filed the charges later revealed to be those against Manafort and Gates.

Reuters reported in August, citing two unnamed sources, that the grand jury had issued subpoenas in connection with the June 2016 meeting Donald Trump Jr. had hosted in Trump Tower, which was attended by several senior campaign aides and Russian lobbyists.

The Financial Times reported later in the month that one Russian lobbyist who attended the meeting, Rinat Akhmetshin, testified before Mueller’s grand jury for several hours on Aug. 11.

And NBC News reported on Tuesday that former Trump campaign aide Sam Clovis, who recently stepped aside from his nomination to be the USDA’s chief scientist, was questioned by Mueller’s grand jury sometime last week. The news reportedly caught the White House off guard.

Clovis, according to court documents and various reports, spoke to former Trump campaign aide George Papadapoulos in emails about the latter’s proposals to bring together Trump campaign officials and Russian government officials. Papadopoulos, according to court records unsealed Monday, pleaded guilty to lying to the FBI about those proposals.

Mueller’s investigation also encompasses at least one other grand jury: A grand jury located in Virginia had pre-dated his appointment as special counsel, and was concerned with potential lobbying violations by Manafort and former National Security Adviser Michael Flynn. It has since been incorporated into his work as special counsel.

Recently, reports emerged that two lobbyists who worked with Manafort on his work promoting the interests of pro-Russian Ukrainian leader Viktor Yanukovych were being investigated by a grand jury: Democrat Tony Podesta — the brother of Hillary Clinton’s campaign chairman — and former Republican congressman Vin Weber, worked with a non-profit called the European Centre for a Modern Ukraine.