Rescuers scrambled to find survivors of the World Trade Center and Pentagon attacks while investigators focused on how the hijackers got into the United States, and who helped them. The Bush administration also said there is evidence the White House and Air Force One were intended targets.
Federal officials say investigators have identified all the hijackers, and estimate there were three to six aboard each of the four passenger planes that crashed in the worst terrorist attack in the United States Tuesday. At least two of the hijackers were on the Immigration and Naturalization Service "watch list," but it's still unclear whether the individuals entered the United States illegally or whether they entered before their names were placed on the list.
Investigators believe at least some of the hijackers were U.S.-trained pilots who entered the country through Canada. State Department officials said they have intelligence information connecting the attacks to indicted terrorist Osama bin Laden.
Most, if not all, of the hijackers were Egyptian or Saudi nationals, sources said.
White House spokesman Ari Fleischer and Secretary of State Colin Powell said there was reason to believe the plane that hit the Pentagon was intended to strike the White House, and that Air Force One was also a target. They refused to elaborate on the "credible information" that led to that belief.
A senior administration official told ABCNEWS that the plane's flight pattern suggested the White House was targeted. The plane circled over the White House and then, for unknown reasons, headed for the Pentagon. There was speculation Tuesday that the fourth plane that crashed in Pennsylvania also targeted Washington.
Getting Worse in New York
In New York, conditions deteriorated late this afternoon when another building at the World Trade Center, Building 5, partially collapsed at One Liberty Plaza. Engineers warned and evacuated rescue workers before the building began to sag. Firefighters, who work separately from the rescue crews, were the only ones allowed in the area amid concerns that there were gas leaks. In addition, rescue workers were evacuated shortly before the remaining seven stories of the South Tower of the World Trade Center fell into the rubble.
Engineers were also concerned about the condition of four other buildings, including the Millenium Hilton Hotel and the 54-story Merrill Lynch Building, which they described as "shakey" to ABCNEWS. Some residents had to be evacuated from their apartments because health officials were concerned about the bad air quality that resulted from the building debris. The impact of Tuesday's attack caused damage to buildings within several blocks of the World Trade Center towers, and rescue crews are concerned that additional collapses could hinder rescue and recovery attempts. On Tuesday, hours after the towers collapsed, Building 7 in the World Trade Center collapsed.
Meanwhile, the United States today received a pledge of international support from its NATO allies, who declared the attacks in the United States can be considered an attack on the whole alliance if it turns out they were directed from abroad.
"An attack on one is an attack on all," NATO Secretary-General Lord Robertson said after the 19 NATO ambassadors decided to invoke Article 5 of the NATO charter for the first time in the alliance's history.