WASHINGTON, April 24 (Reuters) - The Justice Department is closing its investigation into Federal Reserve Chair Jerome Powell, U.S. Attorney Jeanine Pirro said on Friday, removing an obstacle to the confirmation of Kevin Warsh, President Donald Trump's pick to lead the central bank.

Pirro, a Trump ally and the top federal prosecutor in Washington, D.C., said she had instead asked the Fed's internal watchdog, the Office of Inspector General,  to examine cost overruns in renovations of the central bank's Washington headquarters.

"The IG has the authority to hold the Federal Reserve accountable to American taxpayers," Pirro said in a social media post. "I expect a comprehensive report in short order and am confident the outcome will assist in resolving, once and for all, the questions that led this office to issue subpoenas."

Spokespeople for the Fed and the White House did not immediately respond to requests for comment.