U.S. Customs and Border Protection said Friday the agency is investigating an allegation that a Customs agent insisted a journalist admit he writes "propaganda" before returning his passport. Ben Watson, an editor for Defense One, wrote an article on Friday about his confrontation with the agent at Dulles International Airport in northern Virginia.

Watson said he was returning from Denmark Thursday when the agent asked about his occupation. When Watson said he's a journalist, the agent allegedly responded, "so you write propaganda, right?"

Watson said the agent repeated the question several times in a brief back-and-forth before Watson replied, "for the purposes of expediting this conversation" that he writes propaganda. He then was given back his passport.

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A CBP spokesman said Friday the incident is under investigation and agents are held accountable for unprofessional conduct.

Watson has filed a civil rights complaint with the Department of Homeland Security, which oversees CBP.

Earlier this year, CBP apologized to a BuzzFeed News reporter who was aggressively questioned by an agent at a passport control checkpoint. "The immigration agent at JFK just saw that I work for BuzzFeed and just grilled me for 10 minutes about the Cohen story, which was fun given he gets to decide whether to let me back into the country," reporter David Mack, who is from Australia, tweeted about the incident.

In a separate incident in June, freelance reporter Seth Harp said he was detained for several hours in Austin by CBP.