'Serious threat' of terror activity
US President Barack Obama's counter-terrorism adviser has said the administration is taking seriously the intelligence tip of a possible al Qaida plot tied to the 10th anniversary of the September 11 attacks.
The terror network has long sought to attack the US again, and Obama adviser John Brennan said the latest information is specific and from a credible source.
Mr Brennan said investigators are trying to "put the pieces together" and be vigilant. He told Fox News Sunday that the government, in his words, "is taking this very seriously".
Investigators have chased a tip that al Qaida may have sent three men to the US on a mission to detonate a car bomb in either Washington or New York. But officials said they have found no evidence al Qaida has sneaked anyone into the country.