Trump Organization's handling of Mar-a-Lago footage under investigation
Prosecutors investigating Donald Trump's handling of classified documents are examining how his team responded to a request for security footage from his Florida estate.
The Department of Justice requested the video last summer and, according to CNN, investigators are seeking to question several top aides about it.
The investigation, led by Special Counsel Jack Smith, is also assessing whether Mr Trump obstructed the probe.
The former president denies wrongdoing.
The justice department issued a subpoena for the security camera footage last June. The video showed aides moving boxes from a storage room that may have held classified documents, the BBC's US partner, CBS News, previously reported.
But reports suggest investigators are now working to establish why there are gaps in the provided video and why some footage is missing or unavailable.
The investigation has been ramping up in recent weeks as prosecutors seek more information about who had access to classified documents stored at the Mar-a-Lago resort, what Mr Trump told employees about them, and how his team responded to requests for information.
Several witnesses were expected to testify in the investigation on Thursday, including Matthew Calamari Sr, who handles security for the Trump Organization, CNN reported, citing several sources familiar with the investigation.
Mr Smith also reportedly listened in as former Vice-President Mike Pence answered questions before a grand jury for more than five hours last week.
And on Friday, in what appeared to be a significant development, the New York Times reported that an "insider witness" who worked for Mr Trump at Mar-a-Lago had agreed to co-operate with the inquiry.
The witness has not been identified and it is unclear what information they may have provided, although the report suggests they appeared as part of a broader effort to determine whether Mr Trump personally ordered secret documents to be moved from the storage room.
Hundreds of classified files, including some marked Top Secret, were discovered at Mr Trump's Mar-a-Lago estate over the course of the last year.
Ultimately, Mr Smith will decide whether the former president should face criminal charges. Among other statutes, the justice department believes Mr Trump may have violated the Espionage Act by keeping national security information after he left office.
Mr Trump, who is running for president again in 2024, faces several other legal investigations. He was recently indicted in New York over hush money payments made to a porn star. He has pleaded not guilty.
He is also the subject of an investigation in Georgia over his alleged efforts to try and overturn the 2020 presidential election results in the state.