(WASHINGTON) — The Secret Service deleted text messages from Jan. 5 and 6, 2021, after an internal watchdog requested them as part of a review of the department’s handling of last year’s Capitol riot, the watchdog said this week.

A letter sent Wednesday by the Department of Homeland Security Office of Inspector General to the heads of the House and Senate Homeland Security Committees, which was obtained by ABC News, said the messages were deleted “as part of a device-replacement program” despite the inspector general requesting such communications.

“First, the Department notified us that many US Secret Service text messages from January 5 and 6, 2021, were erased as part of a device-replacement program. The USSS erased those text messages after OIG requested records of electronic communications from the USSS, as part of our evaluation of events at the Capitol on January 6,” Joseph Cuffari, the inspector general, wrote.

“Second, DHS personnel have repeatedly told OIG inspectors that they were not permitted to provide records directly to OIG and that such records had to first undergo review by DHS attorneys,” Cuffari wrote. “This review led to weeks-long delays in OIG obtaining records and created confusion over whether all records had been produced.”

The director of communications at the US Secret Service, Anthony Guglielmi, said any insinuation the service intentionally deleted texts is false in a statement Thursday evening.

“The insinuation that the Secret Service maliciously deleted text messages following a request is false. In fact, the Secret Service has been fully cooperating with the Department of Homeland Security Office of Inspector General (DHS OIG) in every respect – whether it be interviews, documents, emails, or texts,” the statement said.

The statement continued that the Secret Service “began to reset its mobile phones to factory settings as part of a pre-planned, three-month system migration. In that process, data resident on some phones was lost,” and that DHS OIG requested electronic communications for the first time on Feb. 26, 2021, after the migration was underway. The agency added that OIG was notified of certain data missing.

The Secret Service also refuted the notion that they were not being cooperative with the DHS investigation.

“To the contrary, DHS OIG has previously alleged that its employees were not granted appropriate and timely access to materials due to attorney review. DHS has repeatedly and publicly debunked this allegation, including in response to OIG’s last two semi-annual reports to Congress. It is unclear why OIG is raising this issue again,” the statement said.

Ohio’s Rob Portman, the top Republican on the Senate Homeland Security Committee, said he was “deeply concerned” over the letter.

“I am deeply concerned by the letter I received from the DHS Inspector General documenting the Department’s delays in producing materials to the Inspector General and its deletion of records following requests by the Inspector General. It is essential that the Department be transparent with its inspector general, Congress, and the American public,” he said in a statement.

The DHS has not yet responded for comment.

Michigan Sen. Gary Peters, the chairman of the committee, echoed that.

“We need to get to the bottom of whether the Secret Service destroyed federal records or the Department of Homeland Security obstructed oversight,” Peters said in a statement. “The DHS Inspector General needs these records to do its independent oversight and the public deserves to have a full picture of what occurred on January 6th. I will be learning more from the DHS Inspector General about these concerning allegations.”

It is unclear whether the messages were deleted intentionally or by accident, though the inspector general’s letter comes as the Secret Service is once again under heightened scrutiny following hearings from the House committee investigating the insurrection.

Recent testimony suggested that former President Donald Trump tried to join his supporters in marching from the Ellipse to the Capitol last year but was stopped by the Secret Service. The agency has since said it will respond on the record to that testimony.

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