New York City security officials say they are not taking any chances after an alleged terror plot targeting the city's subway system was revealed Thursday.

Iraq's prime minister revealed to reporters there was a plot by the militant group ISIS to attack American subway systems.

The White House says officials are working to confirm the validity of the threat. The NYPD says it is also working with the FBI to assess the threat.

Mayor Bill de Blasio and NYPD Commissioner Bill Bratton stressed at a press conference Thursday afternoon that there is no specific threat, even riding the subways to urge calm among city commuters. Security has still been heightened as a precaution, with police and K-9s canvassing train stations.