FBI Warns of New York Subway Terror Attack Tuesday.

US authorities have warned of a possible terror attack mounted by Al Qaeda on the New York city sub way system in the coming days, reports the Associated Press :

An internal memo obtained by The Associated Press says the FBI has received a "plausible but unsubstantiated" report that al-Qaida terrorists in late September may have discussed attacking the subway system.

Anti-terror agencies say they have no specific details to confirm the plot has moved "beyond aspirational planning," but are issuing the alert out of concern that an attack could come during the holiday season," warns the memo, which is dated Tuesday.