"Mayor Michael Bloomberg said the FBI had alerted him to "a specific threat to our subway system," which had come from overseas but had already been partially thwarted, while some officials cast doubt on the credibility of the threat.
"We have never had before a specific threat to our subway system. This is the first time we have had a threat with this level of specificity," Bloomberg told a news conference. "We have done and will continue to do everything we can to protect this city." See The Guardian for more on this.
"Despite the differing takes on the seriousness of the threat, New York officials mobilized police officers to begin looking through commuters' bags, briefcases, baby strollers and luggage."
So now commuters in New York have the joy of facing even more security measures than we faced and are still facing, to some extent, on the Tube each day.
"An estimated 4.5 million passengers ride the New York subway on an average weekday. The system has more than 468 subway stations. In July, the city began random subway searches following the London train bombings."