Did you know these facts about 9/11 terror attacks?

The US is marking the 20th anniversary of the September 11 attacks. The series of four terrorist attacks orchestrated by al-Qaida that targeted the twin towers of the

World Trade Centre

in New York and the

Pentagon

shook the US to the core.

Nearly 3,000 people were killed, including more than 2,600 at the

World Trade Center

, 125 at the Pentagon, and 265 on the four planes.

More than 6,000 were injured.

Take a look at some staggering facts about the 9/11 attack:

The

New York City Fire Department

lost 343 firefighters, almost half the number of on-duty deaths in the department's 100-year history.

There were 75 firehouses in which at least one member was killed. The

Fire Department

of the City of New York (FDNY) also lost its department chief, first deputy commissioner, one of its marshals, one of its chaplains, as well as other administrative or specialty personnel. The battalion chief of Battalion 1 witnessed the crash into the North Tower of the World Trade Center and immediately radioed a multiple alarm incident. Over the course of the next three hours, 121 engine companies, 62 ladder companies and 27 fire officers were deployed to the scene.



The youngest passenger on the hijacked jets was Christine Hanson on

United Airlines

Flight 175.

She was 2 and on her first trip to Disneyland. Initially, Christine's parents were scheduled to fly out on September 10. But they moved their flight at the last minute because her father, a vice president of sales for a software company, had a work conflict, says Christine’s grandmother, Eunice Stylos Hanson.




The hijackers were mostly Saudi nationals who entered the United States and attended flight training schools without raising alarms.
According to CIA Director George Tenet “the system was blinking red,” but despite

White House

briefings on the Osama Bin Laden threat, intelligence agencies and domestic law enforcement failed to share crucial information. Post this the American government attacked Afghanistan which was the base for al-Qaida. However, none of the nineteen hijackers were Afghan nationals. Mohammed Atta, an Egyptian, led the group, and fifteen of the hijackers originated from Saudi Arabia.



Over 1,100 people were arrested in connection with the attacks.

According to

PBS

news service quoting Justice Berman, 1,182 people were arrested till November 5. The judge says he is unclear how many but they were given a list of 750 people arrested on immigration charges, and some additional unknown number have been arrested as material witnesses. Since 2002, roughly 780 detainees have been held at the American military prison at Guantánamo Bay, Cuba. Now, 39 remain. Of those, 12 have been charged with war crimes in the military commissions system — 10 are awaiting trial and two have been convicted. In addition, 17 detainees are held in indefinite law-of-war detention and are neither facing tribunal charges nor being recommended for release. And 10 are held in law-of-war detention but have been recommended for transfer with security arrangements to another country.



Weeks after the 9/11 attacks, a series of letters containing anthrax, a highly lethal virus, were delivered to newsrooms and congressional offices which killed five people.

The refined nature of anthrax raised fears that the biological attacks are state-sponsored. The White House and US intelligence agencies also blamed Iraqi dictator Saddam Hussein but findings later refuted the claims. Later, the

FBI

pinned the blame on American scientist Bruce Ivins. After Ivins commits suicide in 2008, the FBI closed the case.



Fires continued to burn in lower Manhattan for 99 days after the attack.
The pile stabilized enough that construction crews could start using excavators and other heavy equipment. But the site was still dangerous. Underground fires continued to burn for months. Every time a crane moved a large chunk of debris, the sudden rush of oxygen intensified the flames. Downtown Manhattan reeked of smoke and burning rubber, plastic and steel. The site was awash in harmful fumes and toxic dust. Especially in the days immediately after the towers fell, when investigators estimated that only 20 percent of the workers at the site had masks that would protect their lungs, the air was filled with diesel exhaust, pulverized cement, glass fibers, asbestos, silica, benzene from the jet fuel and lead.

1.5 million working hours during 261 days were spent removing the debris at the World Trade Center site.

The cleanup and recovery efforts at Ground Zero lasted for more than a year, with crews working around the clock. Construction workers found human remains in several places near the site of the Twin Towers in 2006, while the Environmental Protection Agency spent several years working to clean toxic dust out of downtown apartments. Still, dust and debris from the September 11th attacks will likely continue to affect downtown Manhattan for years; still, the impressive scale and speed of the cleanup work was a testament to the dedication of the workers and volunteers at the site.