Pressure is mounting on President Joe Biden to give further details about the classified documents found at his Delaware home and a Washington office he once used. An independent lawyer, or special counsel, has been appointed by the justice department to investigate whether these papers were mishandled. There are still more questions than answers about the files. Here's a look at some of the things we still don't know. What's in them? Mr Biden has said he does not know what's in the recovered papers. And until we know more about what they contain, it's difficult to state exactly how serious this is. Some details, however, have started to emerge. Sources told CNN and the New York Times that the first set of 10 classified documents included briefing materials on foreign countries - including Ukraine, Iran and the United Kingdom - from Mr Biden's time as vice-president. And according to CNN, these documents were mixed in with other non-classified papers, including details about the funeral of Beau Biden, the president's son, who died in 2015. It also reported that some of the documents were labelled as top secret, the highest level of classification. We know less about the second set of documents. On Thursday, Mr Biden's personal lawyer issued a statement that said the files were "Obama-Biden Administration records" meaning these, too, date back to his eight years as vice-president. The White House later said a search for any remaining classified documents had been completed. Who had access? A massive bureaucracy that manages the basic operations of the federal government (called the General Services Administration) is responsible for the transition of power in the White House. This herculean task includes getting the new president and vice-president in and getting the departing ones - and their files - out.

But it's still unclear who may have handled these files in the seven years since Mr Biden ended his tenure as vice-president. The problem with politicians and classified files The only hints we may have are where they were found. The first set of files was discovered by Mr Biden's lawyers in what the White House described as a locked closet of the president's office at the Penn Biden Center for Diplomacy and Global Engagement, a think tank in Washington. The second tranche was found later in the garage of Mr Biden's home in Wilmington, Delaware. A single-page document was discovered in an adjacent room. Investigators will no doubt want to know who had access to these places and how securely the files were stored. Congressional Republicans have demanded to see visitor logs for Mr Biden's homes, arguing that the discovery of the files at one of his residences is a national security risk.