Sources: Grand jury Subpoenas Issued in Relation to Trump Jr., Russian Lawyer Meeting

Grand jury subpoenas have been issued in connection with a June 2016 meeting that included President Donald Trump’s son, his son-in-law and a Russian lawyer, two sources familiar with the matter told Reuters on Thursday.

The sources added that special counsel Robert Mueller had convened a grand jury in Washington to investigate allegations of Russian meddling in the 2016 U.S. election.

Russia has loomed large over the first six months of the Trump presidency, with U.S. congressional panels also investigating the Russian election interference that U.S. intelligence agencies believe was meant to tilt the vote in Trump’s favor.

Moscow denies any meddling and Trump denies any collusion by his campaign, while regularly denouncing the investigations as political witch hunts.

Mueller’s use of a grand jury could give him expansive tools to pursue evidence, including issuing subpoenas and compelling witnesses to testify. The impaneling of the grand jury was first reported by the Wall Street Journal.

A grand jury is a group of ordinary citizens who, working behind closed doors, considers evidence and potential criminal wrongdoing that a prosecutor is investigating and decide on whether charges should be brought.

U.S. stocks and the dollar weakened following the news, while U.S. Treasury securities gained.

Earlier this week, Reuters reported that Mueller, who was appointed special counsel in May, brought a former U.S. Justice Department official to join his investigative team.

Greg Andres started on Tuesday, becoming the 16th lawyer on the team.