WASHINGTON, D.C. — Three prosecutors from U.S. Attorney Jeannine Pirro's office were turned away from the Federal Reserve's headquarters in Washington, D.C., on Tuesday after making an unannounced visit and requesting a tour of the central bank's ongoing renovation project. Pirro's deputies said they wanted to check on progress in the yearslong renovation of the Federal Reserve's historic buildings overlooking the National Mall.

The attempted visit is the latest development in a Justice Department investigation into Fed Chair Jerome Powell's congressional testimony about the renovation project. The investigation became public in January when Powell announced that subpoenas had been served on the Federal Reserve.

Powell has characterized the probe as tied to the central bank's monetary policy decisions. "The threat of criminal charges is a consequence of the Federal Reserve setting interest rates based on our best assessment of what will serve the public, rather than following the preferences of the president," Powell said.

Chief Judge James Boasberg of the U.S. District Court for Washington, D.C., blocked the subpoenas that Pirro's office had served on the Federal Reserve on March 13. "The Government has produced essentially zero evidence to suspect Chair Powell of a crime," Boasberg wrote.

The Federal Reserve's outside counsel wrote to Pirro's office stating that Boasberg had concluded the interest in the renovation project was pretextual and that any challenge to that finding should go through the courts. The counsel also asked that prosecutors commit not to seek to communicate with the Fed outside the presence of counsel.

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

Kevin Warsh is President Donald Trump's nominee to succeed Powell as chair of the Federal Reserve.