Added security remains in Lower Manhattan
The crowds of mourners have mostly left following this morning's ceremony at Ground Zero, but an added security presence remains in the area, after officials received a credible but unconfirmed threat against targets in the city.
Traffic has reopened in Lower Manhattan, but police are still stationed in the area.
Officials say they are looking for three men, two of who are American citizens, who may be plotting on detonating car bombs on a bridge or inside a tunnel.
Thousands attended the ceremony this morning at Ground Zero.