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Investigation: Remaining on alert

Attorney General John Ashcroft speaking at a recent news conference.

SUMMARY:

A security alert issued was a "reiteration" of the alert issued to law enforcement agencies October 11, Homeland Security chief Tom Ridge said, and it should be taken seriously but should not stop people from living normal lives.

At least one of the suspected hijackers who allegedly crashed a passenger jet September 11 purchased his plane ticket from a travel agent in a northern New Jersey town near where the alleged ringleader of the attacks was spotted this summer.

President Bush called for tighter immigration policies to more easily track suspected terrorists visiting the United States.

UPDATE:

Earlier this week, Attorney General John Ashcroft announced Monday that intelligence sources had gathered "credible" information that more terror attacks could be launched on the United States in the next few days. White House Press Secretary Ari Fleischer said the information gathered came from "multiple sources" but lacked "specificity." (Full story)

"America understands and hopefully appreciates," Ridge said, "when there is that kind of information, we share it no matter how incomplete it may be."

On October 11, the FBI issued an alert warning of possible terrorist attacks on American soil or against U.S. international interests. No such attack took place, but Ridge said "we'll never know" if the alert may have "thwarted or frustrated an attack."

In a separate development, Hani Hanjour paid cash on August 31 -- 11 days in advance -- for a one-way ticket on American Airlines Flight 77 from Washington Dulles to Los Angeles, the plane that crashed into the Pentagon, at ATS Travel in Totowa, New Jersey, according to two employees of the independently owned agency who spoke to CNN on the condition of anonymity. (Full story)

Totowa is the neighboring town to Paterson, where, CNN has previously reported, Hanjour was one of at least four suspected hijackers who shared a one-bedroom apartment for $650 a month, rent paid in cash each month by Hanjour, according to the building's landlord.

Elsewhere, President Bush vowed to "tighten up" loopholes in immigration policies he said have allowed terrorists to slip into this country and attack U.S. citizens. "Our job now is to find the evil ones and bring them to justice," Bush said.

In announcing the formation of the Foreign Terrorists Tracking Task Force, Bush said authorities would check on immigrants who enter the United States on student visas to make sure they actually attend school.

"We're going to start asking a lot of question that heretofore have not been asked," he said. (Full story)

•  Summary   •  Update   •  Key questions   •  Who's who   •  Impact

CNN.COM SPECIAL REPORT  CNN NewsPass Video  Agencies reportedly got hijack tips in 1998  MORE STORIES Intelligence intercept led to Buffalo suspects Report cites warnings before 9/11  EXTRA INFORMATION Timeline: Who Knew What and When? Interactive: Terror Investigation Terror Warnings System Most wanted terrorists What looks suspicious? In-Depth: America Remembers In-Depth: Terror on Tape In-Depth: How prepared is your city?  RESOURCES On the Scene: Barbara Starr: Al Qaeda hunt expands? On the Scene: Peter Bergen: Getting al Qaeda to talk

VIDEO CNN's Lisa Barron reports that since the September 11 attacks more companies are verifying credentials of potential business partners (October 21) Play video (QuickTime, Real or Windows Media)

KEY QUESTIONS:

What tactics are being used to get people in custody to talk about any knowledge they may have of the September attacks?

What avenues are international investigators pursuing to trace the source of funding for the suspected hijackers? Click here for more.

What clues about the September 11 attacks have U.S. investigators learned from the hundreds of arrests made?

How will the expansion of law-enforcement powers affect Americans' civil liberties? Click here for more.

How long can suspects be held, and on what charges are they being held? Click here for more.

What groups are U.S. investigators focusing on, and what are their aims? Click here for more.

WHO'S WHO:

George W. Bush: U.S. president

Colin Powell: U.S. secretary of state Click here for more

Condoleezza Rice: National security adviser Click here for more

John Ashcroft: U.S. attorney general

Robert Mueller: FBI director Click here for more

George Tenet: CIA director. Click here for more

Osama bin Laden: U.S. authorities have named bin Laden, a wealthy Saudi exile living in Afghanistan, as the prime suspect in masterminding the September 11 attacks. Click here for more

IMPACT:

Information gained from the investigation could lead to fundamental changes in U.S. security and intelligence systems, as well as surveillance laws.