Federal prosecutors have obtained an audio recording of former President Donald Trump acknowledging that he held onto a classified Pentagon document about a potential attack on Iran, according to media reports.

The revelation of the recording, first reported by CNN Wednesday, potentially means that Trump knew he possessed classified material after leaving the White House — undermining his argument thus far that the document was declassified.

Reports of the audio recording were also confirmed by The Washington Post and The New York Times. POLITICO has not independently verified the existence of the recording.

The recording was made during a meeting held at Trump’s golf club in New Jersey in July 2021, according to CNN, where people were helping Trump’s former chief of staff, Mark Meadows, write a memoir. One of Trump’s aides routinely taped the interviews he gave for books being written about him that year, according to The New York Times.

A Trump spokesperson in a statement to POLITICO called reports of the recording “political persecution.”

“Leaks from radical partisans behind this political persecution are designed to inflame tensions and continue the media’s harassment of President Trump and his supporters,” the spokesperson said. “The DOJ’s continued interference in the presidential election is shameful and this meritless investigation should cease wasting the American taxpayer’s money on Democrat political objectives.”

The Justice Department is currently investigating Trump’s handling of classified material, though he denies wrongdoing. The majority of the investigation into Trump’s handling of classified material has centered on documents at his Mar-a-Lago residence.

The audio recording from summer 2021 is described as an “important” piece of evidence in a possible case against Trump, according to an anonymous source in the CNN report.

James Trusty, a lawyer representing Trump in the case, told CNN Wednesday night that Trump’s position was that he had declassified the material he took with him upon leaving office.

“When he left for Mar-a-Lago with boxes of documents that other people packed for him that he brought, he was the commander in chief,” Trusty said. “There is no doubt that he has the constitutional authority as commander in chief to declassify.”