Airport screeners pulled aside four of the Sept. 11 hijackers after they set off metal detectors before boarding the flight that later crashed into the Pentagon, a surveillance video reveals.

The video, which was obtained by The Associated Press, shows the screener at Washington Dulles International Airport hand-checking a carry-on bag of hijacker Nawaf al-Hazmi.

He and his brother, Salem, who both set off the detectors, are then allowed to continue on to American Airlines Flight 77.

Two other hijackers, Khalid al-Mihdhar and Majed Moqed, also set off metal detectors, the video shows. Moqed set off a second alarm and had to be manually checked with a handheld metal detector. Moqed and al-Mihdhar were then allowed to continue.

Fifth hijacker doesn't set off detector

Hani Hanjour, believed to have been the hijacker who piloted Flight 77, did not set off a metal detector as he passed through Dulles security that morning, according to the video.

The video, released a day before the commission investigating the 9/11 attacks releases its final report, does not show knives or other sharp objects.

Investigators on the 9/11 commission have said the hijackers at Dulles were believed to be carrying utility knives either personally or in their luggage.

But at the time, those items could legally be carried aboard planes.

The Associated Press said it obtained the video from the Motley Rice law firm, which is representing some survivors' families suing the airlines and security industry over their actions in the Sept. 11 attacks.