HONG KONG — Tens of thousands of dollars in cash. Documents listing locations of United States Cyber Command outposts. A passcode-protected thumb drive, hidden behind a sock in the toe of a shoe.

According to the Justice Department, these are among the items that United States agents found over the years while searching the luggage of Ron Rockwell Hansen, a former Defense Intelligence Agency case officer, as he flew numerous times between the United States and China. Mr. Hansen, 58, a fluent Mandarin speaker who first visited China in 1981, has allegedly received at least $800,000 in “funds originating from China” since May 2013.

On Saturday, Mr. Hansen was arrested in Seattle and charged with attempted espionage, in what appears to be another high-profile mole hunt by F.B.I. investigators intent on uncovering Chinese spying against the United States.

“His alleged actions are a betrayal of our nation’s security and the American people and are an affront to his former intelligence community colleagues,” John C. Demers, the assistant attorney general for national security, said in a statement posted on the Justice Department’s website on Monday.