A lawyer for Donald Trump refused to report to the National Archives that the former president had turned over all Oval Office documents as required out of concern that the claim was a lie.

Earlier this year, Trump returned 15 boxes of federal government records from his Mar-a-Lago resort home to the National Archives, and he directed one of his lawyers, Alex Cannon, to inform the agency that the boxes contained all the documents taken from his time in office.

Cannon, who was facilitating the records’ return, refused Trump’s request because he “told others he was not sure if other documents were still at the [Florida resort] and would be uncomfortable making such a claim”, The Washington Post reported.

Faced with Cannon’s refusal, Trump later directed a statement in February to aides saying that all his documents from his time in office had been returned to the National Archives and Records Administration. But federal agents later learned Trump still had government documents at Mar-a-Lago, including some records marked with the highest level of classification.

The FBI seized those documents during its 8 August search of Mar-a-Lago.

On Monday, the National Archives released a letter that revealed they had alerted lawyers for Trump in May 2021 that the former president’s correspondence with Kim Jong-un, North Korea’s leader, were missing along with two dozen boxes of other records.

The US justice department has been investigating whether Trump’s unauthorized retention of such government secrets violated multiple laws, including the Espionage Act.

Trump’s aides turned over a set of documents in June to the justice department. The August search of Mar-a-Lago produced the seizure of thousands of documents, among them dozens of classified records.

When archives officials opened the initial 15 boxes they recovered in January, they found a large volume of documents with classified markings and notified the justice department, which set off the chain of events leading the criminal investigation into Trump.

Legal wrangling between the justice department and Trump’s lawyers has slowed that investigation down.

Trump has claimed, without evidence, that the FBI planted evidence during its search of Mar-a-Lago residence. The federal judge presiding over those claims, Aileen Cannon, granted Trump’s request for an independent official known as a “special master” to review the seized documents before the case proceeded further.

That review process is expected to last until between the end of November and the middle of December.