An ally of former U.S. President Donald Trump, Joe diGenova, announced on Thursday that he has resigned from his role leading a Department of Justice (DOJ) investigation into whether former law enforcement and intelligence officials conspired against Trump. DiGenova told the Associated Press that he “did in fact resign” and called his time serving Trump and the DOJ an “honor and a privilege.” However, he did not explain the reasons behind his departure. DiGenova had been brought back to the DOJ in April to oversee an investigation into former government officials who have scrutinized Trump in various criminal inquiries over the past decade. His resignation comes just five months after his return, introducing uncertainty into the ongoing probe. The investigation had recently picked up speed, with new subpoenas being issued to demand testimony before a federal grand jury in Florida, where the case has been centered. DiGenova, 81, previously served as the U.S. attorney for the District of Columbia during the Reagan administration. A long-time Trump supporter, he had previously requested then-Attorney General Pam Bondi to appoint him to this role. He has publicly and repeatedly claimed that Trump was the target of a conspiracy by the intelligence community. Despite his efforts, no charges have been filed yet, and it remains unclear whether any will be. The investigation has focused heavily on one of Trump’s main complaints: a U.S. intelligence assessment that Russia interfered in the 2016 presidential election on Trump’s behalf. Trump and some of his supporters have long criticized this conclusion as a “deep state” plot to undermine his victory. However, multiple government investigations, including those by a DOJ special counsel and the DOJ’s own inspector general, have concluded that Russia did indeed interfere extensively to help Trump win. The investigation had been ongoing for over a year before diGenova was appointed, and it had moved in fits and starts. His appointment came after a career national security prosecutor, who had played a key role in the investigation, was replaced after expressing doubts about the legal merits of the case. DiGenova’s departure now raises questions about the direction and momentum of the probe, which has yet to yield any concrete results or charges.