Two of the three people suspected to be behind Thursday’s “credible” terror threat against New York could be Americans, sources told NBC News Friday. But intelligence officials were quick to say that the information about the suspects was vague. They said they believe that two of the suspects were Americans who flew in through Dubai while the other suspect flew in through Europe, or all three might have been smuggled into Pakistan so their travel records wouldn’t be public. The source only offered partial names, and the names were said to be non-Western names that are “common in the Middle East,” the source said. U.S. Secretary of State Hillary Clinton confirmed Friday that the threat came from al Qaeda, while New York escalated security measures in the wake of the 10th anniversary of the Sept. 11 terrorist attacks.