Enlarge By Richard Drew, AP A New York City Police officer walks a subway platform in midtown on Wednesday. NYPD spokesman Paul Browne said they have received an unsubstantiated report and as a result have "deployed additional resources in the mass transit system." NEW YORK  The federal government has warned state and local agencies about "plausible but uncorroborated information" that al-Qaeda may be planning a holiday-season attack on area transit systems here. Neither the Department of Homeland Security nor the FBI has specific information to confirm that a potential plot has developed beyond planning, according to a statement DHS posted on its website. The warning cited intelligence that al-Qaeda may have discussed in late September the targeting of New York-area transit systems. The DHS-FBI warning was issued as a routine precautionary heading into the holiday season so that state and local agencies can make decisions about whether to beef up security, DHS said in its statement. Security in New York's subways and commuter trains was strengthened after terrorist bombings on rail and bus systems in Madrid in 2004 and London in 2005 killed 243 people. New York police routinely conduct random checks of passengers and their belongings. Metropolitan Transportation Authority, which operates New York's subways, said Wednesday that commuters should be cautious but not fearful. "The MTA is aware of an unsubstantiated report of terrorist threats against transit properties during the holiday season," spokesman Jeremy Soffin said. "We are already on high alert and are always on a heightened state of readiness during this season. We have been working closely with local, state and federal law enforcement to increase police presence throughout our transportation system. As always, we ask that our customers remain alert and report any suspicious activity or packages, but there is no reason to be alarmed." No adjustments are being made to the nation's terror threat level or specifically for transit systems, DHS said. However, transit passengers in larger metropolitan areas such as New York may see an increased security presence in coming days, including uniformed and plainclothes behavior detection officers, federal air marshals, canine teams and security inspectors. The Transportation Security Administation has deployed federal air marshals to the New York area and will work with local transit systems, including the Long Island Rail Road and Metro North commuter rail systems, said Christopher White, a TSA spokesman. Both are run by the MTA. Metro North connects Manhattan to Westchester County and Connecticut. The LIRR is the nation's largest commuter-rail system. Generally, the air marshals are both plainclothes and uniformed, wearing blue nylon jackets with "Air Marshal" on the back in white writing. The Port Authority of New York and New Jersey also is involved in handling this incident. The authority runs the Port Authority Trans-Hudson subway, which connects lower Manhattan and New Jersey. "As a routine matter, we remind the public to be both thoughtful and vigilant of their surroundings, and to report anything suspicious to authorities," DHS said in a statement on its website. Discussing the reported threat, New York Rep. Peter King, the top Republican on the House Homeland Security Committee, said authorities "have very real specifics as to who it is and where the conversation took place and who conducted it." "It certainly involves suicide bombing attacks on the mass transit system in and around New York and it's plausible, but there's no evidence yet that it's in the process of being carried out," King said. Frank reported from Washington. Contributing: Associated Press Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more