Law enforcement sources tell CBS News that investigators have determined that Times Square bomb suspect Faisal Shahzad used the "hawala" system in plotting the attack, concealing the movement of money by using couriers and bypassing banks or other financial institutions.

The hawala system is a courier system used by terrorists and criminals to conceal the flow of money without raising red flags among law enforcement.

It's a type of informal banking system frequently used by family and tribes - at times legitimately.  There are numerous ways to do it. One is to have couriers come to the United States carrying less than $10,000 cash to remain under the amount that must be declared at U.S. Customs. That courier usually gives the cash to a "hawala dar," a person who controls the money - who then gives it to the intended person.

Complete Coverage: Terrorism in the U.S.

It can also be used as an informal money-wiring system. For example, if you wish to give a relative  $200 in New York and you are located in Pakistan, you may give it to a family member in Pakistan who knows someone in New York. The family member in Pakistan tells the person in New York that it's okay to give the your relative $200 because his relative in Pakistan "gave me the $200 and I have it in hand."

Law enforcement sources said it's unclear whether Shahzad used the hawala system in part or totally in obtaining financing for the attack, including the purchase of the SUV he allegedly packed with explosive material and parked in Times Square and the purchase of his ticket to Dubai from Kennedy Airport to escape authorities.

In a related development, U.S. federal agents conducted a series of raids in the Massachusetts, New York and New Jersey, arresting three people in connection to the Times Square bomb investigation.

Law enforcement sources tell CBS News the raids are aimed at possible money remitters, though authorities have said it's possible those detained had passed money to Shahzad unwittingly.

As investigators probe a possible link between Shahzad and the Pakistani Taliban, one of the critical aspects is confirming the flow of money - who handled the money, who were the facilitators, to determine if they were associates or members of the Pakistan Taliban.

So far, that analysis is leading investigators in the direction of the Pakistani Taliban. Investigators are continuing to focus on the identities of those individuals with the help of Pakistani intelligence and law enforcement.

by Bhakti Mamtora, CBS News Investigative Unit

The psychological cost of a terrorist attack in the heart of Times Square is incalculable. But a CBS News analysis has found the cost to make the car bomb that Faisal Shahzad allegedly left in Times Square last Saturday night is surprisingly inexpensive.

Special Section: Terrorism in the U.S.

The most expensive component was the vehicle itself. Shahzad is said to have purchased the Nissan Pathfinder on Craigslist for $1,300 cash.

But the actual bomb components cost less than $800 - that's roughly the cost of a 42 inch flat screen TV.

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Accused New York Times Square bomber Faisel Shahzad, 30, was drowning in debt, raising questions about how he managed to have wads of cash at his disposal to help carry out his alleged plot.

Shahzad made at least a dozen return trips back and forth between the United States and Pakistan in the last 11 years.

Before taking his last trip to Pakistan in June of 2009, Shahzad worked for the Affinion Group of Norwalk, CT as a Junior Analyst.  The position pays an estimated annual salary between $55,000 and $80,000.

Yet, as CBS News first revealed, Shahzad came under scrutiny by the Department of Homeland Security for bringing into the U.S. more than $80,000 in "cash or cash instruments" between 1999 and 2008.

But clearly Shahzad had financial problems. He had a $200,000 mortgage on his 3-bedroom Shelton, CT home that he unsuccessfully tried to sell for three years. Then, in February of 2009, he took out an additional home equity loan for $65,000. But, it appears he never intended to repay that loan. Just the next month, he began defaulting on both loans.

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Sources tell CBS News that would-be Times Square bomber Faisal Shahzad appeared on a U.S government travel travel lookout list - Traveler Enforcement Compliance System (TECS) - between 1999 and 2008 because he brought approximately $80,000 cash or cash instruments into the United States.

TECS is a major law enforcement computer system that allows its approximately 120,000 users from 20 federal agencies to share information. The database is designed to identify individuals suspected of or involved in violation of federal law.

CBS News Exclusive Picture of Shahzad

The system has been recently called inefficient by members of Congress. In late March, Senator Joe Lieberman of Connecticut and Susan Collins of Maine criticized the system in a letter to DHS, writing that, "Current functionality does not allow interoperability among databases, fast searching of information, modern interfaces for users of the system, or sufficient security to protect critical terrorist travel data."

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CBS News has learned that Senator Charles Grassley (R-IA) is launching an inquiry into how Faisal Shahzad became a naturalized U.S. citizen in 2009 despite multiple law enforcement investigations into his background over the last 10 years.

Grassley sent Department of Homeland Security Secretary Janet Napolitano a letter today asking for the "Alien" file for Shahzad and his family members and for everyone who has been a reference or a sponsor for the terror suspect.

An Alien or "A" file includes visa and travel history, financial and personal information as well as any derogatory information from law enforcement. Grassley wants to know if this file was in the hands of the official who approved Shahzad's citizenship.

Grassley also wants Shahzad's arrival forms that he filled out each time he re-entered the United States and whether or not he sponsored other individuals to become citizens.

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A photo obtained exclusively by CBS News shows the would-be Times Square bomber Faisal Shahzad with friends in Times Square, less than 100 yards from the spot where he abandoned an explosives-laden SUV Saturday.

The photo shows Faisal Shahzad standing on the far right with his wife, Huma Mian, and several other unidentified people. Sources tell CBS News the photo is believed to have been taken a year and a half to two years ago.

To date, most images of Shahzad have come from the Orkut.com social site, where his wife had a profile.

PICTURES: Faisal Shahzad, Times Square Bomb Suspect
PICTURES: Times Square Car Bomb
Faisal Shahzad's Near Escape
Shahzad's Story
The Pakistan Connection
Faisal Shahzad's Motive a Mystery
No-Fly List Procedures Changed
Lawmakers Ask How Suspect Boarded Plane
"Unguided Missiles" Pose New Threat
53 Hours to Arrest
How Close Until He Got Away?
Shahzad's Connecticut Associates under Scrutiny

When a suspected terrorist is arrested, reporters turn to their neighbors and community to find out more.  But a day in Faisal Shahzad's Bridgeport, Conn. community indicates the man had few local connections.

Visits to local Islamic centers and many local businesses in Bridgeport revealed little about the man who has confessed to driving and explosives-laden SUV into the middle of Times Square. In fact, no one seemed to know him.

But the manager of the local Halal Meat and International Foods in Bridgeport, Mohammed Abid quickly recognized Shahzad's picture as a regular customer saying Shahzad came in about twice a month over three or four years to buy ground beef, chicken and chicken legs. But Abid had no idea that his faithful customer had been arrested for a potential terrorist attack until we told him. He said Shahzad always came alone and was "very nice and quiet". Abid did not know Faisal had a family in the United States.

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In federal court in Manhattan, Faisal Shahzad, the man accused of trying to explode a car bomb in a Nissan Pathfinder in Times Square on Saturday night, was charged with five counts, including trying to explode a weapon of mass destruction.

Shahzad was arrested as he tried to leave the country Monday night at John F. Kennedy International airport. After the arrest, prosecutors say Shahzad admitted receiving bomb-making training in Waziristan, Pakistan.

Read the complaint

According to the complaint, Shahzad admitted that he "brought the Pathfinder to Times Square - and attempted there to detonate it."

Special Section: Terrorism in the U.S.

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U.S. authorities were tracking the Faisal Shahzad, 30, as he boarded Emirates Airline flight at Kennedy Airport bound for Dubai. The suspect made a cash payment for a one-way flight reservation, which triggered an alert by the airline to U.S authorities.

CBS News' Bob Orr said that Emirates Airline "notified the Department of Homeland Security and the rest of the federal government that they got a last minute request for a purchase- a one way purchase in cash - from an individual who wanted to go to Dubai. Those are all red flags. The airline said to the FBI and others this is suspicious and in fact, a short time later, the man was found on the plane and apprehended."

Administration officials said that Shahzad was placed on the federal no-fly list after authorities identified him, but the addition was too recent for the systems to automatically trigger an alert. U.S. Customs and Border Protection (CBP) instead resorted a more conventional "be on the lookout" type of alert to prevent Shahzad from fleeing.

Following is the exchange between the control tower and Emirates flight as it was on the runway and preparing for takeoff  with Shahzad, and called back to the gate:

CONTROLLER

151058 Emirates 202 heavy, Kennedy tower, Runway 22 right position. 151101 Actually, I have a message for you to go back to the gate immediately 151105 so make the left turn when able. 151106

PILOT

151107 So...22 -202, turning left here. 151112

CONTROLLER

151113 Alright, Emirates 202, make the left turn onto echo left alpha back to the ramp. I don't exactly why but you can call your company for the reason. 151121

PILOT

151122 Will do that. Left onto echo, then onto alpha and back to the gate - via golf?

More on the Times Square Terror Plot:

CBSNews.com Special Report: Terrorism in the U.S.

Shahzad Appeared to be Family Man, Neighbors Say

Times Square Link could Force Pakistan's Hand

Shahzad Tried to Return to Pakistan

Gun Found in Bomb Suspect's Car, Sources Say

NYC Bomb Investigation Focus 

Bomb Suspect: How Was He Caught?