NEW YORK, NY September 22, 2009 —The MTA has stepped up police presence at "key locations," like Grand Central Terminal, in light of the ongoing probe into a possible terrorist plot. Even so, the agency says there's no credible threat to the city's subways and commuter trains. Meanwhile, federal officials issued bulletins, reminding local police nationwide that entertainment complexes, sports stadiums, and hotels are favored targets of terrorists. The NYPD says it has not increased police presence at these sites. Mayor Bloomberg says that's because New York City is always on guard.

BLOOMBERG: We have been at heightened level for a long time, and I think everything they recommended, we already do.

Separately, law enforcement officials said a Colorado man may have been planning with others to detonate backpack bombs on New York City trains in a terrorism plot similar to past attacks on London's and Madrid's mass-transit systems.