US Attorney General Merrick Garland speaks during a news conference at the Justice Department on Wednesday in Washington, DC.
CNN  — 

The Justice Department has begun investigating the handling 15 boxes of White House records, including classified information, taken to Mar-a-Lago after former President Donald Trump left office, a source familiar with the matter tells CNN.

This comes as the Justice Department is blocking the National Archives from sharing details on the boxes with Congress, which has launched its own investigation.

In a letter that the House Oversight Committee disclosed on Thursday, Archives General Counsel Gary Stern said the agency was unable to respond to the panel’s request for more information, based on the Archives’ “consultation” with the Justice Department.

After receiving the March 28 letter from the National Archives, also known as NARA, House Oversight Committee Chairwoman Carolyn Maloney, a Democrat from New York, reached out to Attorney General Merrick Garland requesting additional information as to why the Justice Department is preventing the Archives from cooperating with the panel.

“I write today because the Department of Justice is preventing NARA from cooperating with the Committee’s request, which is interfering with the Committee’s investigation,” she wrote in a letter dated Thursday. “By blocking NARA from producing the documents requested by the Committee, the Department is obstructing the Committee’s investigation.”

Maloney says that the committee “does not wish to interfere in any manner with any potential or ongoing investigation by the Department of Justice.”

However, she says the committee has not received any explanation for why the Justice Department is preventing the Archives from providing information to the committee, which is investigating potential violations of the Presidential Records Act by Trump.

The FBI and Justice prosecutors routinely conduct reviews when classified materials are found to have been handled or stored in ways that don’t meet government requirements. Moving and storing classified information to the former President’s private club in Florida would appear to fall outside those requirements.

It is also common practice for the Justice Department to limit information that government agencies share with Congress while an investigation is ongoing.

The Justice Department declined to comment. The Archives did not immediately respond to a request for comment.

In February, Garland responded to questions about the Archives assessment that classified material was found in the Mar-A-Lago boxes. He said the Archives had informed the Justice Department “and we will do what we always do under these circumstances: look at the facts and the law and take it from there.”

This story and headline have been updated with additional developments Thursday.