WASHINGTON ( CNN ) -- Federal authorities have received a `` plausible but unsubstantiated '' report that al Qaeda may have discussed targeting transit systems in or around New York , the Department of Homeland Security said . Al Qaeda suicide bombers could target New York City subways , federal security officials say . `` These discussions reportedly involved the use of suicide bombers or explosives '' on subway or passenger rail trains , according to a joint Homeland Security and FBI statement issued Tuesday . `` We have no specific details to confirm that this plot has developed beyond aspirational planning , but we are issuing this warning out of concern that such an attack could possibly be conducted during the forthcoming holiday season , '' the statement said . The uncorroborated information indicates that al Qaeda may have discussed in late September targeting New York transit systems , Homeland Security spokeswoman Laura Keener said . She said the memo was issued as a precaution so local officials could make decisions appropriate for their areas . Although no adjustment is being made to the national threat level , she said , transit passengers in large metropolitan areas such as New York may see increased security in the days to come . That presence might include uniformed or plainclothes security officers , federal air marshals , canine teams and security inspectors , Keener said . New York police also are deploying additional resources on the city 's mass transit systems as a precaution , said a statement by Deputy Commissioner Paul Browne . `` It is not uncommon for the department to receive threat information and to adjust our resources accordingly , '' Browne said . The FBI received the information through a channel that has provided reliable information in the past , so the agency is taking the threat seriously , counterterrorism sources said . The FBI and Department of Homeland Security said they had no further information on the threat . `` We are working closely with the U.S. intelligence community , state and local law enforcement and homeland security officials to vet and corroborate this reporting , and will continue to investigate every possible lead . We 'll provide updates as we obtain further information , '' the statement said . The public should remain vigilant and report suspicious activity to authorities , it said . Al Qaeda has the means to launch such an attack , said CNN senior international correspondent Nic Robertson , who has covered al Qaeda extensively since before the September 11 attacks . `` The al Qaeda-affiliated groups are still willing to make these attacks , '' Robertson said . `` What we 've seen in the past is , they 've become capable of making these homemade bomb devices with detonators and exploding them by cell phones or by suicide bombings . '' However , he said , it also would be possible for al Qaeda to plant false information . `` They would love to sort of create fear when they 're not actually capable of creating a strike . ... I 've seen it myself , in Afghanistan . You get the Taliban out there on the ground , and they 're very capable of knowing that the troops are listening to them , and feeding and sowing false information trails saying , 'We 're over on this part of the hill ' when they 're nowhere near it . They 're very capable and knowledgeable about feeding false information . ''
Suicide bombers may be used against New York transit , government says . Joint FBI , Department of Homeland Security statement says plot unconfirmed . Attack could be planned for holiday season , statement says .