United States Attorney for Utah John Huber has been investigating whether the FBI abused its authority in surveilling a former top aide to then-GOP presidential nominee Donald Trump and whether federal officials should have probed deeper into allegations of Hillary Clinton’s ties to the sale of U.S. uranium rights to a Russian-controlled company.

U.S. Attorney General Jeff Sessions said in a letter to some congressional leaders Thursday that he appointed senior federal prosecutors — led by Huber — to review concerns raised by Republicans that the FBI ignored those issues while focusing on investigating the Trump campaign for possible collaboration with Russia.

Sessions said that the reviews by federal prosecutors like Huber mean there’s no need right now for appointment of a second special counsel, as Republican lawmakers had requested.

“We understand that the Department is not above criticism and it can never be that the Department conceals errors when they occur,” Sessions wrote to Senate Judiciary Chairman Chuck Grassley, House Judiciary Chairman Bob Goodlatte and House Oversight and Government Reform Chairman Trey Gowdy, all Republicans.

The uranium deal referred to in Sessions’ letter refers to a 2010 purchase of a controlling interest in Uranium One by a Russian subsidiary. The acquisition went through when Hillary Clinton was secretary of state, and her department was among nine involved in allowing the deal.

The nonprofit Clinton Foundation had accepted large donations from people with ties to Uranium One, and former President Bill Clinton had taken a big speaking fee from a Russian company.

Trump talked about the “uranium scandal” in October, shortly before special counsel Robert Mueller’s investigation into Russian meddling in the election produced its first criminal charges.

“I think that’s your Russia story,” Trump said at the time. “That’s your real Russia story. Not the story where they talk about collusion, and there was none. It was a hoax. Your real Russia story is uranium.”

The nonpartisan organization FactCheck.org conducted an independent review of the allegations and concluded that there was nothing to them.

“There is no evidence that donations to the Clinton Foundation from people with ties to Uranium One or Bill Clinton’s speaking fee influenced Hillary Clinton’s official actions,” said FactCheck.org.

It appears from the letter that Huber has been conducting his investigation from Utah at least since November.

“I am confident that Mr. Huber’s review will include a full, complete and objective evaluation of these matters in a manner that is consistent with the law and facts,” Sessions wrote. “I receive regular updates from Mr. Huber and upon the conclusion of his review, will receive his recommendations as to whether any matters not currently under investigation should be opened, whether any matters currently under investigation require further resources, or whether any matters merit the appointment of a special counsel.”

GOP Congress members wrote Sessions last year, asking for investigations into a raft of issues, including Clinton’s mishandling of classified information and post-election accusations by Trump that he was wiretapped by the Obama administration. They also requested probes into leaks of classified information that unmasked the identities of people on Trump’s campaign and transition teams; the FBI’s “apparent reliance” on a Clinton campaign-funded investigation of the Trump campaign; and “any and all potential leaks” originated by former FBI Director James Comey.

Sen. Orrin Hatch, R-Utah, said Huber brings the independent perspective of a federal prosecutor “who has spent his career far removed from the politics of Washington.”

“I am confident that Mr. Huber will perform these duties with the utmost integrity, and I look forward to learning the results of his work at the appropriate time,” Hatch said in a written statement.

Huber, who was appointed by President Barack Obama in 2015 with the strong backing of Hatch and Sen. Mike Lee, has twice been confirmed to the office by the Senate. He is the vice chairman of the Attorney General’s Office Advisory Committee.