Classified documents have been found at former US Vice-President Mike Pence's home in the latest discovery of secret papers.

The records were discovered by a lawyer for Pence at his Indiana home last week and were handed over to the FBI.

This is happening as special counsels are already investigating President Joe Biden and ex-President Donald Trump's handling of secret documents.

Meanwhile, Trump is being investigated criminally for allegedly mishandling files.

The FBI arrived at the former Vice President's house to acquire the documents, circumventing "normal protocols" and asking for "direct custody", according to lawyers.

The Presidential Records Act requires that White House records be transferred to the National Archives when an administration ends. Regulations demand that such files be securely stored.

At the end of Donald Trump's administration, a "limited number of documents carrying secret markings" were "inadvertently packaged and carried" to Pence's house, his lawyer stated in a letter released by US media.

The latest development emerged after Pence sought legal counsel from professionals in handling secret documents "out of an abundance of caution."

"He asked for help after it became public that documents with classified markings were found in President Joe Biden's Wilmington residence," the letter read.

A flashback

The first batch of 10 papers was discovered on January 9 at the President's Penn Biden Center for Diplomacy in three or four boxes and was dated between 2013 and 2016, and contained documents related to Ukraine, Iran, and the UK. 

The second batch was found in the garage of his Wilmington Residence, with an additional one-page document found in one of the residence's rooms. 

The third batch was found in Biden's residence in Wilmington, Delaware.