The White House is expressing relief that the 10th anniversary of the Sept. 11 terrorist attacks has passed without incident, despite the investigation into a credible but unconfirmed threat focused on New York or Washington.

Spokesman Jay Carney says the al-Qaida terrorist network is known for striking on significant dates, like 9/11, and that the administration obviously is relieved that anniversary observances around the country took place without incident.

Carney says authorities continue to treat seriously the still unconfirmed intelligence tip of a possible al-Qaida plot tied to Sunday's anniversary.