Prosecutors from U.S. Attorney Jeanine Pirro's office visited the Federal Reserve's headquarters unannounced Tuesday and attempted to gain access to the building's ongoing renovations, which are the subject of a months-long active criminal investigation, according to a source familiar with the matter and a letter reviewed by CBS News.

The two prosecutors and an investigator from Pirro's office were denied access to the site, and were given contact information for the Fed's legal team, the source said.

The decision by the federal prosecutors to visit the renovation site is highly unorthodox. A similar move by Pirro's predecessor to visit New York Attorney General Letitia James's house drew allegations from James' attorney that the office ran afoul of the rules of professional conduct for attorneys and internal Justice Department policies, which call for fair and even-handed treatment in criminal cases. 

The investigation into Fed Chair Jerome Powell centers on a pricey years-long project to renovate the Fed's headquarters and was opened by the U.S. Attorney's Office in D.C. in November, according to court filings. The Fed is not funded through tax dollars.

In January, Powell revealed that the Federal Reserve had received grand jury subpoenas from the Justice Department as part of a criminal investigation into him. The central bank chief said the subpoenas threatened a criminal indictment related to his testimony before the Senate Banking Committee in June 2025. 

The chair said the investigation centered on his testimony about the renovation project, which has cost about $2.5 billion so far. But Powell — who has drawn President Trump's ire for declining to slash interest rates at a rapid clip — argued the probe was part of an effort to intimidate the Fed. The investigation has not resulted in any criminal charges.

In March, Chief Judge James Boasberg of the U.S. District Court for the District of Columbia quashed the pair of subpoenas, saying they were a pretext to pressure Powell into voting for lower interest rates or resigning. Powell's term as Fed chair ends in May, but he can remain a member of the central bank's board — and keep voting on monetary policy — until early 2028.

"There is abundant evidence that the subpoenas' dominant (if not sole) purpose is to harass and pressure Powell either to yield to the President or to resign and make way for a Fed Chair who will. On the other side of the scale, the Government has offered no evidence whatsoever that Powell committed any crime other than displeasing the President," Boasberg wrote in his ruling, adding that in his opinion, "these subpoenas are mere pretexts."

The Justice Department asked Boasberg to reconsider his decision, but he denied that request earlier this month.

In a letter to the prosecutors reviewed by CBS News, the Fed's outside legal counsel, Robert Hur, wrote that the men appeared at the Fed without prior notice Tuesday, told staff they wanted to "check on progress" of the renovations and asked for a "tour" of the site.

"As you know, Chief Judge Boasberg has concluded that your interest in the Federal Reserve's renovation project was pretextual," Hur wrote. "Should you wish to challenge that finding, the courts provide an avenue for you; it is not appropriate for you to try to circumvent it."

Hur served as the Justice Department special counsel who investigated former President Joe Biden's handling of classified documents from his time as vice president, and found that no criminal charges were warranted in the case.

In a statement to CBS News, Pirro said that "Any construction project that has cost overruns of almost 80% over the original construction budget deserves some serious review. And these people are in charge of monetary policy in the United States?"

A spokesperson for the Fed declined to comment.

The prosecutors' surprise visit to the headquarters renovation was first reported by the Wall Street Journal.

The prosecutors, Carlton Davis and Steven Vandervelden, are two allies of Ms. Pirro who were also involved in a failed bid to indict six sitting congressional Democrats who taped a video urging members of the military to reject "illegal orders." In that case, the grand jury unanimously rejected the charges, CBS News previously reported.

The investigator who accompanied the two prosecutors to the Fed's renovation site, Matthew Fox-Moles, is assigned to a special prosecutions team in Pirro's office, a source familiar with the matter told CBS News.

Last summer, Mr. Trump visited the Fed's headquarters personally to tour the renovation project. Powell and Mr. Trump donned hard hats and, while television cameras rolled, openly argued about the scope of the project's cost overruns.

The ensuing criminal probe has caused difficulties for Mr. Trump's effort to replace Powell as Fed chair when his term ends. Republican Sen. Thom Tillis of North Carolina, who sits on the Senate Banking Committee, has sharply criticized the investigation and said he will not vote to advance Mr. Trump's nominee for the powerful job, Kevin Warsh, until the Justice Department's investigation wraps up.

Tillis reacted on X to news of Tuesday's visit from Pirro's office by posting a photo of the Three Stooges.