The documents may have been overlooked because they were with other old trip binders, and would be hard to spot without skimming through each of the pages, multiple sources told CNN.
Such briefing binders often include details about the people an official is going to meet during their international visit and the information included can range from basic background knowledge on foreign leaders to more confidential intelligence about them.
The classification marking of the papers was on a “lower level”, the sources told CNN, and there were reportedly no documents found with the highest levels of classification known as “sensitive compartmented information” (SCI) and “secret”.
The FBI and the Justice Department’s National Security Division have launched an investigation into how the documents ended up in Mr Pence’s home. His lawyer told CNN that the FBI requested to pick up the documents marked classified that evening, to which he agreed. FBI agents at the field office in Indianapolis recovered the documents from his home.
Mr Pence’s representative Greg Jacob wrote to the National Archives that a “small number of documents bearing classified markings” were inadvertently transferred and boxed to his Indiana home.
The revelations come as president Joe Biden faces criticism for having classified documents from his time as Barack Obama’s vice president at his office at the Penn Biden Center at the University of Pennsylvania and his home in Wilmington, Delaware.
More documents were found at Mr Biden’s home in Delaware during the weekend amid a detailed search of his home.
Mr Biden’s personal attorney said the president offered “full access to the president’s home” and “personally handwritten notes, files, papers, binders, memorabilia, to-do lists, schedules, and reminders going back decades,” though the search was not publicised “in accordance with its standard procedures”.
That news, in turn, came after the FBI executed a search warrant at Mr Trump’s home at Mar-a-Lago in Palm Beach to recover documents from his presidency.
Republicans have sought to draw a comparison between Mr Trump and Mr Biden, saying that the FBI unduly searched Mr Trump’s home while it has not done the same for Mr Biden. House Republicans have requested visitor logs of Mr Biden’s home in Wilmington, even though no such logs exist.
In response, attorney general Merrick Garland appointed special counsel Robert Hur to oversee the investigation into classified documents at Mr Biden’s home and office.