Federal agents collected a trove of electronic devices and other materials during an FBI raid at former National Security Adviser John Bolton’s residence last month, newly unsealed court records show, confirming for the first time an open espionage investigation into his handling of government secrets.

The 13-page warrant return filed in federal court on Thursday included a list of items seized during the Aug. 22 search on President Donald Trump’s first-term adviser, including a white binder labeled “Statements and Reflections to Allied Strikes,” four folders of typed documents labeled “Trump I – IV,” a hard drive, and multiple USB drives. Agents also took several laptops, including a Dell Precision Tower and a Dell Inspiron 2370.