Law enforcement agencies kept roads around the Capitol closed on Tuesday evening as they investigated a vehicle driven by a man claiming that he had been exposed to anthrax.
The man, who was driving a white four-door pickup near the National Mall, was detained and hospitalized, U.S. Park Police said.
He drove onto the mall between Third and Fourth streets near the Capitol Reflecting Pool.
Areas around Third Street from Constitution to Pennsylvania avenues and Fourth Street from Independence to Constitution avenues remained closed for about two hours after the incident was first reported, D.C. police said.
Test results for anthrax exposure conducted on the scene were negative but the man and the police officers who made contact with him went through a decontamination procedure.
Police said the man, whom they did not identify, called Capitol Police to warn of the exposure and said there was anthrax in the vehicle. The man said he saw the substance being spread on a field in Virginia and collected it to warn others of the danger.