US authorities have discovered that President Joe Biden and former president Donald Trump had classified documents in their possession long after they should have handed them over, sparking a political furore and federal investigations.
Mr Biden's legal team said it had found classified documents dating back to his time as vice president at his home in Wilmington, Delaware, as well as in an office in Washington. A special counsel has been appointed to investigate the matter.
Last year, US authorities said Mr Trump had held hundreds of government documents after his presidency ended in January 2021 and the National Archives and Records Administration had been trying to retrieve them.
Mr Trump and his team could face charges related to breaching the Espionage Act, which prohibits gathering and disseminating sensitive government documents, as well as obstruction of justice.
But how sensitive are the documents discovered? What classification levels are there and who can access them? The National takes a look.
What documents were found by Biden's team?
The White House said early this month that the President's legal team had found some classified material at his office at the Penn Biden Centre for Diplomacy and Global Engagement in November.
Mr Biden's aides then conducted searches of his homes in Wilmington and Rehoboth Beach in Delaware — “the other locations where files from his vice presidential office might have been shipped in the course of the 2017 transition”, special counsel to the President, Richard Sauber, said in a statement.
Lawyers this month found “a small number of additional Obama-Biden administration records with classified markings” in a garage at Mr Biden's home, along with a one-page document in an adjacent room.
Mr Biden's team did not reveal what kind of classification the documents had.
What documents did Trump have?
The former president kept hundreds of government documents after his presidency ended.
An FBI document justifying the agency's search of Mr Trump's Mar-a-Lago home in Palm Beach, Florida in August said the National Archives had retrieved 15 boxes from his team in May. Classified documents were found in 14 of them.
A total of 184 classified and top-secret documents were found, with 67 were marked confidential, 92 secret and 25 top secret. Some documents included sensitive foreign intelligence, as well as “human intelligence” sources.
The FBI warrant stated that agents had removed about 20 boxes from Mar-a-Lago. The agency said it had identified about 100 classified documents within the boxes that held 11,000 government files.
What classification levels are there? What does 'various classified/TS/SCI' mean?
With Mr Biden's documents, CNN reported that “top secret” and “SCI” labelling were found on files in his Washington office, while the President's legal team did not confirm classification levels on the documents.
In the Trump case, there were “confidential”, “top secret” and “SCI” labelling on files retrieved by the National Archives and through the FBI search.
“SCI” stands for “sensitive compartmented information”, which covers materials that contain the most sensitive information. Those documents are closely protected and only viewable in approved facilities.
“TS” stands for “top secret” and it is the next step down from SCI.
If seen by the wrong people, SCI-labelled and top-secret documents could cause irreparable damage to US national security.
“Secret” and “confidential” documents necessitate lower security clearances, meaning more people have access to them and they would do less damage to national security if revealed.
Who can view these files?
Documents labelled “top secret” require the highest level of security clearance.
SCI material can be top secret but the documents are treated differently in how they are protected, housed and viewed.
Clearance to access-specific SCI files are an add-on to top-secret security clearance. Being approved to view a specific SCI document does not mean a person can view another elsewhere.
Federal employees or private contractors doing work for the US government can receive security clearance through a lengthy, formal background check.
US presidents, vice presidents and members of Congress do not have to undergo security screenings and are not required to have security clearance.
About four million people in the US have security clearance of some level.