New York Police Department officers keep watch in part of the Times Square subway station in New York City. [Chris Hondros/Getty Images/AFP]

Speaking to the Associated Press on condition of anonymity, an authority briefed on the matter says the threat may be directed at passenger rail lines running through New York.

In particular the federally supported passenger service or the Long Island Rail Road -- both particularly busy with holiday travellers during Thanksgiving.

News of the terrorism alert was received with mixed reactions by subway riders who have become accustomed to increased security since the 9/11 attacks.

Many say the threat will likely NOT change their travel plans.

Elise Haigezia, said, "I don't think it would change my mind just because riding the train is kind of so essential to getting from point A to point B, regardless of where you are in the city, but it would definitely be in the back of my mind."