The National Archives and Records Administration last month retrieved 15 boxes of documents and other items from former President Donald Trump’s Mar-a-Lago residence because the material should have been turned over to the agency when he left the White House, Archives officials said Monday.

The recovery of the boxes from Trump’s Florida resort raises new concerns about his adherence to the Presidential Records Act, which requires the preservation of memos, letters, notes, emails, faxes and other written communications related to a president’s official duties.

Trump advisers deny any nefarious intent and said the boxes contained mementos, gifts, letters from world leaders and other correspondence. The items included correspondence with North Korean leader Kim Jong Un, which Trump once described as “love letters,” as well as a letter left for his successor by President Barack Obama, according to two people familiar with the contents.

Archives officials confirmed the transfer, which occurred in mid-January, following publication of a version of this story by The Washington Post earlier Monday. The agency said in a statement that “these records should have been transferred to NARA from the White House at the end of the Trump Administration in January 2021,” and that Trump representatives are “continuing to search” for additional records.

“The Presidential Records Act is critical to our democracy, in which the government is held accountable by the people,” Archivist of the United States David Ferriero said in the statement. “Whether through the creation of adequate and proper documentation, sound records management practices, the preservation of records, or the timely transfer of them to the National Archives at the end of an Administration, there should be no question as to need for both diligence and vigilance. Records matter.”

Discussions between the Archives and the former president’s lawyers that began last year resulted in the transfer of the records in January. One person familiar with the materials said Trump advisers discussed what had to be returned in December. Some of the people familiar with the transfer spoke on the condition of anonymity to reveal internal details.

A spokesman for Trump did not respond to a request for comment.

The Archives has struggled to cope with a president who flouted document retention requirements and frequently ripped up official documents, leaving hundreds of pages taped back together – or some that arrived at the Archives still in pieces. Some damaged documents were among those turned over to the House select committee investigating the Jan. 6, 2021, attack on the U.S. Capitol by a pro-Trump mob.

“The only way that a president can really be held accountable long term is to preserve a record about who said what, who did what, what policies were encouraged or adopted, and that is such an important part of the long-term scope of accountability – beyond just elections and campaigns,” presidential historian Lindsay Chervinsky said.

From a national security perspective, Chervinsky added, if records and documents are not disclosed, “that could pose a real concern if the next administration is flying blind without that information.”

Rep. Stephanie Murphy, D-Fla., a member of the Jan. 6 committee who did not have knowledge of the Mar-a-Lago transfer, said the overall records situation reflected the “unconventional nature of how this White House operated.”

“That they didn’t follow rules is not a shock,” Murphy said. “As for how this development relates to the committee’s work, we have different sources and methods for obtaining documents and information that we are seeking.”

The recovery of documents from Trump’s Florida estate is just the latest example of what records personnel described as chronic difficulties in preserving records in the Trump era – the most challenging since Richard Nixon sought to block disclosure of official records, including White House tapes.

All recent administrations have had some Presidential Records Act violations, most often involving the use of unofficial email and telephone accounts. White House documents from multiple administrations also have been retrieved by the Archives after a president has left office.

Bill and Hillary Clinton had to return thousands of dollars worth of gifts they took with them when they left the White House in 2001. Shortly after George W. Bush was sworn in as Bill Clinton’s successor, the Post reported that the Clintons left the White House with $28,000 in furnishings that they said were personal gifts but that were actually given to the National Park Service for the White House permanent collection.

But personnel familiar with recent administrations said the Trump era stands apart in the scale of the records retrieved from Mar-a-Lago. One person familiar with the transfer characterized it as “out of the ordinary. … NARA has never had that kind of volume transfer after the fact like this.”

Trump himself was unconcerned about the records act, according to former advisers.

“Things that are national security sensitive or very clearly government documents should have been a part of a first sweep – so the fact that it’s been this long doesn’t reflect well on (Trump),” said a lawyer who worked in the White House Counsel’s Office under Obama. “Why has it taken for a year for these boxes to get there? And are there more boxes?”

While the law requires that presidents preserve records related to an administration’s activities, the Archives has very limited enforcement capabilities. The Presidential Records Act operates on the basis of a “gentlemen’s agreement,” as one Archives official phrased it.

Stephen Gillers, a New York University law professor and constitutional scholar, along with other legal experts point to the potential for enforcement that could take place via federal records laws. But several said they thought such action would be unlikely.

“There is a high bar for bringing such cases,” said Charles Tiefer, former counsel to the House of Representatives who teaches at the University of Baltimore School of Law.

Typically, he said, records preservation proceeds by mutual agreement with the occupant of the White House, staff and archivists. “But if there is willful and unlawful intent” to violate the law then the picture changes, he said, with penalties of up to three years in jail for individuals who willfully conceal or destroy public records.

“You can’t prosecute for just tearing up papers,” he said of Trump. “You would have to show him being highly selective and have evidence that he wanted to behave unlawfully.”

Some former Trump aides say they do not believe Trump was acting with criminal intent.

“I don’t think he did this out of malicious intent to avoid complying with the Presidential Records Act,” one former Trump White House official said. “As long as he’s been in business, he’s been very transactional and it was probably his longtime practice and I don’t think his habits changed when he got to the White House.”