By EVAN PEREZ, CAM SIMPSON and SIOBHAN GORMAN
WASHINGTON -- U.S. authorities didn't pursue leads that might have brought alleged Christmas Day bomber Umar Farouk Abdulmutallab under further scrutiny, according to congressional investigators and U.S. officials.
The State Department forwarded Mr. Abdulmutallab's name to a basic U.S. terrorist watch list earlier this month, but didn't revoke his visa after Mr. Abdulmutallab's father alerted U.S. officials to his son's potential radicalization. His purchase of a $2,800 plane ticket with cash also didn't set off alarm bells.
The case highlights a failure of the terrorist watch-list system to adapt to the evolving threat from al Qaeda, said one senior U.S. counterterrorism official. Intelligence reports have said for years that a growing threat comes from al Qaeda sympathizers who may not have a direct connection to its leadership.
U.S. terrorism defenses still rely on data that associate suspects with known al Qaeda operatives, rather than scrutinizing behavior that could indicate terrorist planning, the official said.
The administration has launched a review of its screening, including the series of watch lists designed to prevent potential terrorists from traveling to the U.S. The review likely will include whether to require foreign airlines to report cash purchases of tickets overseas, a Homeland Security official said Monday.
One area of inquiry is whether the State Department should have revoked Mr. Abdulmutallab's multiple-entry visa after his father on Nov. 19 came to the U.S. Embassy in Abuja, Nigeria, and reported that his son might have extremist ties in Yemen. A revocation could have forced Mr. Abdulmutallab to reapply, giving authorities a chance to interview him.
Instead, State Department officials say, the day after the father's visit, the agency put a note in Mr. Abdulmutallab's internal State Department file that would trigger an investigation if the Nigerian applied for a new visa in the future.
Although the State Department has the authority to independently revoke a visa, the agency rarely makes such decisions on its own. Instead, it relies on investigations by the National Counterterrorism Center, the multiagency clearinghouse for terrorism information.
The warning by Mr. Abdulmutallab's father should have been combined with information from airline personnel, such the suspect's purchase of his ticket with cash and his carrying only a backpack for an international flight. That behavioral profile "doesn't mean he should be on the no-fly list, but he should be checked out," the counterterrorism official said.
Embassy personnel sent a report about Mr. Abdulmutallab to intelligence and counterterrorism officials in the U.S., as required by law. That prompted intelligence officials to create a record in the National Counterterrorism Center's TIDE database, a repository of 560,000 individuals that many agencies rely on to create their own, smaller watch lists.
But the data didn't merit further action because they didn't meet the threshold of "reasonable suspicion," said one U.S. intelligence official. Only if Mr. Abdulmutallab had been elevated to a narrower watch list would he likely have been stopped and questioned.
Another U.S. security flag that should have been triggered, according to airline industry experts, was one designed to discriminate between air travelers who are known customers -- who pay with credit cards and whose data match previously used information -- and those who are less known, such as those who pay with cash.
On Dec. 16, Mr. Abdulmutallab paid cash in Accra, Ghana, for a reservation, and provided no contact information, according to Nigerian authorities. U.S. systems designed to scrutinize cash-ticket purchases weren't triggered, people briefed on the probe say, so Mr. Abdulmutallab didn't get a secondary screening in Amsterdam.
A Homeland Security official said cash purchases don't have to be reported from overseas because they are common, especially in poor countries.
Mr. Abdulmutallab carried a valid U.S. visa printed into a Nigerian passport equipped with the latest security features, Nigerian authorities said.
The bombing attempt could also prompt scrutiny from lawmakers of the Air Marshals program, which was beefed up after the Sept. 11, 2001, terror attacks. According to Rep. Peter King (R., N.Y.), there were no marshals on the Christmas Day flight, nor on the same flight two days later where another passenger disruption occurred.
—Susan Carey contributed to this article.
Write to Evan Perez at evan.perez@wsj.com, Cam Simpson at cam.simpson@wsj.com and Siobhan Gorman at siobhan.gorman@wsj.com
