The security presence on the New York City subway system has been significantly increased in the wake of Thursday’s dramatic announcement by the city’s mayor Michael Bloomberg that New York’s subway system is facing what he called a “specific threat.” Bloomberg and other officials said the threat was specific and could involve explosives smuggled onto trains via briefcases or baby strollers. Here is New York Police Commissioner Ray Kelly: “The New York Police Department and the Federal Bureau of Investigation have received information which indicates that the city subway system may be the target of a terrorist attack in the coming days. While the information has not been fully corroborated, it has been deemed of sufficient concern for the police department to enhance its counter-terrorism coverage of the subway system and to advise the public of the threat and to ask its assistance in reporting immediately any suspicious individual or activities to police or transit personnel.”