Washington, D.C., police converged on the National Mall on Tuesday afternoon after a man drove onto the downtown's grassy park and claimed he had anthrax in his truck.
Witnesses said the man exited his white pickup truck and spoke on his mobile phone before he was detained by police.
Soon afterward, he was taken to a decontamination tent while a robot inspected the vehicle.
Police remained in the area while determining the nature of the threat.
