“Chairman Neal has asked Treasury OIG to inquire into the process by which the department received, evaluated and responded to the committee’s request for federal tax information,” said Delmar. “We are undertaking that inquiry.”

The inquiry will likely take “several weeks to a couple of months but that’s a front-end guess,” he said.

“Obviously, it’s a priority.”

The development comes as Neal is suing Trump in federal court to enforce a subpoena for the records under a 1924 law allowing the heads of Congress’s tax committees to examine anyone’s private tax information. Trump has defied a decades-old tradition of presidents voluntarily releasing their returns.

Treasury Secretary Steven Mnuchin has refused to turn over the filings, saying Democrats do not have a legitimate legislative reason for seeking the documents. The administration says Democrats merely want to search Trump’s records for potentially embarrassing information.

Neal, however, argues that he needs the documents to examine how thoroughly the IRS audits presidents and vice presidents, which is routine after they are elected.

A district court in Washington has scheduled a Nov. 6 hearing on a bid by Trump’s lawyers to have the case dismissed.

The Treasury Department did not immediately respond to a request for comment.

Neal asked Delmar for the probe earlier this week.

“I want to be assured that Treasury, including the Internal Revenue Service (“IRS”), is enforcing the law in a fair and impartial manner and no one is endeavoring to intimidate or impede government officials and employees carrying out their duties,” Neal said in a letter to Delmar.

Neal asked Delmar to identify everyone within Treasury and the IRS, and anyone outside the agencies, who was “involved in the handling of my requests and all related decisions.”