The FBI is searching the Maryland home of former Trump administration national security adviser John Bolton as part of an investigation into the handling of classified documents, a person familiar with the matter said Friday.

The person was not authorized to discuss the investigation by name and spoke on the condition of anonymity to The Associated Press.

Messages left with a spokesperson for Bolton and the White House were not immediately returned. A lawyer who has represented Bolton had no immediate comment Friday.

Bolton served as Trump’s third national security adviser for 17 months and clashed with him over Iran, Afghanistan and North Korea.

The first Trump administration had unsuccessfully sought to block the publication of a Bolton book that it said contained classified information.

On his first day back in office this year, Trump, a Republican, revoked the security clearances of more than four dozen former intelligence officials, including Bolton.

Bolton was also among a trio of former Trump officials whose security details were cancelled by Trump earlier this year.