Federal Reserve Chair Janet Yellen is balking at turning over some of the documents ordered by a key House lawmaker in his investigation of a possible leak of market-sensitive information.

Yellen has told Rep. Jeb Hensarling, R-Texas, who heads the House Financial Services Committee, that she can't provide some documents sought by his subpoena because that could jeopardize a criminal investigation by the Justice Department.

The move escalated a months-long battle between the Fed chair and the lawmaker over an alleged leak in 2012 of interest-rate information to a financial newsletter.

Hensarling issued a subpoena to the Fed last month, saying it had failed to adequately respond to the panel's questions and requests for documents.

The Fed says its own investigation found no evidence that sensitive information was deliberately leaked.