A pilot who runs an executive jet company has been arrested after U.S. agents found more than $600,000 in his aircraft during a stop in Puerto Rico.

Court documents show that Khamraj Lall was the co-pilot on a flight to Guyana when agents from U.S. Customs and Border Protection and Homeland Security Investigations searched the aircraft when it stopped to refuel.

U.S. law requires amounts over $10,000 to be declared and Lall and the two others on board reported carrying about $12,000.

A Homeland Security spokeswoman says the source of the money is under investigation.

Lall is being held on suspicion of intent to evade currency reporting.

The Guyana native is CEO of Gainesville, Florida-based Exec Jet Club, LLC. A person answering the phone at the company Wednesday declined comment.