Rescue crews are working through the darkness tonight in a desperate search for survivors of the worst terrorist act in the nation's history.
In an unprecedented barrage of terrorist attacks, both World Trade Center towers collapsed after being struck by two different hijacked planes Tuesday morning, and authorities have evacuated Lower Manhattan amid a cloud of choking debris.
The full extent of the casualties is not yet known. One city official says that the number of fatalities could exceed 10,000.
Up to 300 firefighters are missing with many presumed dead, and approximately 33 police officers are unaccounted for.
Mayor Rudolph Giuliani said late Tuesday night that rescue workers were attempting to reach a small group of people trapped in the basement of one of the World Trade Center buildings.
Two Transit Authority police officers were rescued from the rubble of the Seven World Trade Center building earlier in the evening.
The mayor said that rescue workers have brought in banks of lights to aid in the search for survivors in the rubble. More than 1,000 emergency workers, including National Guard troops are on the scene.
Approximately 54,000 people worked in the 110-story World Trade Center towers, and authorities do not yet know how many of them were still in the buildings at the time of their collapse.
The unprecedented attack began shortly before 9 a.m. when a commercial airliner, under the control of hijackers, crashed into Tower Number 1 near the top of the building. Fifteen minutes later, another hijacked plane struck the other tower.
Two World Trade Center, which was hit second, completely collapsed nearly an hour after the initial impact, sending thousands of panicked people on the street running for cover as a cloud of debris engulfed Lower Manhattan. One World Trade Center crumbled to the ground about 30 minutes later, completely erasing the landmark from the New York City skyline.
Rescue crews were on the scene soon after the plane crashes and may not have been aware the structures were unstable, since the damage and fire seemed to be isolated to the top of the towers after the crashes.
Around eight hours later, at 5:30 p.m., the 47-story Seven World Trade Center building collapsed as well. That building had housed the Office of Emergency Management's multi-million dollar bunker, which would have been the coordination center for the massive rescue operation in such a crisis.
A third plane struck the Pentagon 40 minutes after the attack in New York, destroying one of the fives sides of the military headquarters and causing extensive casualties. A fourth plane also crashed near Pittsburgh, Pennsylvania, but it is unclear where that airliner was headed at the time of the crash.
A total of 266 people were on board the four crashed flights.
The White House was evacuated after terrorist threats were received and all other federal offices were cleared as a precaution as well.
So far no one has claimed responsibility for the attacks.
It appeared the situation was contained after the first fireball explosion at the World Trade Center, when the crash of the second plane was broadcast on live television reports around 15 minutes later. The impact seemed contained again and people stood on the street watching the smoke for almost an hour before the sudden and unexpected collapses.
Immediately after the plane crashes, witnesses reported seeing a plane's wheel as well as shoes from some victims fall to the ground several blocks from the towers. Fire burned in both towers until the collapse, black smoke billowing out of the gaping holes left in each building by the planes' impact.
The towers were evacuated after the crashes but an unknown number of people were still trapped inside when the buildings crumbled. People could be seen jumping from windows in the skyscrapers to certain death before the collapse.
Hundreds of people hit by flying debris and other injured flooded nearby hospitals for treatment. Nearly 1,500 more were treated for less serious injuries.
Bodies were scattered over the scene of the collapse and buried in two feet of rubble that covers surrounding streets.
In an unprecedented move, the FAA has grounded all flights nationwide until at least noon on Wednesday in response to the attacks. Most international flights on their way to the U.S. were directed to Canada to land.
The U.S. Navy has also sent two aircraft carriers to New York City to provide air cover in precaution against any further possible attacks.
The National Guard has been called in to aid and relieve city rescue personnel.
The New York City primary election scheduled for Tuesday has been postponed and polls are closed.
The attacks come eight years after the World Trade Center was attacked by terrorists in a bombing that killed six people and injured more than 1,000 others in 1993. One of the bombers convicted in that attack was set to be sentenced Wednesday.
The attacks also took place near the anniversary of the 1978 Camp David peace accords, fueling speculation that the attacks could be related to the violence in the Mideast.
Word of the attacks sparked cheering and celebration among Palestinians in East Jerusalem. Palestinian leader Yasir Arafat, however, publicly condemned the attacks.
Afghanistan's Taliban rulers condemned the attacks in New York and Washington, saying accused terrorist mastermind Osama bin Laden - a fugitive from U.S. justice hiding within their borders - was not behind them.
A London-based journalist says bin Laden's followers warned three weeks ago that they would carry out a huge and unprecedented attack on U.S. interests. He says he didn't take the threat seriously because such warnings are often given but not carried out.