(CBS) The FBI gave serious consideration to letting suspected al Qaeda member Jose Padilla walk out of Chicago's O'Hare International Airport last month to see where he would lead them and who he might meet. But after determining there was no one to meet him in the airport, and no one waiting outside, agents made the arrest because they simply didn't want to take the chance of losing him, reports CBS News Correspondent Jim Stewart.

That was among the newest revelations Tuesday in the investigation into whether Padilla, a U.S.-born felon who took the Islamic name Abdullah al Muhajir, was actively planning to build and explode a 'dirty bomb' – a crude explosive linked to radioactive material that would cause both panic and low-level contamination of any area where it was set off. Authorities have said that Padilla and possible other collaborators where in the "initial planning stages" of a plan to acquire and detonate a dirty bomb, possibly in Washington D.C.

Padilla had a perfectly valid replacement passport issued by the U.S. consulate in Karachi, Pakistan, when he arrived at O'Hare on May 8. He told officials he was "returning home to visit his son and mother in Chicago."

But Padilla lied, officials said, when he told agents he had never been in Afghanistan. And was vague about the $10,000 in U.S. currency he was carrying, which officials determined Padilla picked up in Zurich, Switzerland, enroute to the United States.

Investigators say the money was provided by al Qaeda to conduct a target scouting trip in the U.S. and seek our possible industrial and medical radioactive materials to use in the construction of a radiological, or "dirty" bomb. There is no indication Padilla had anyone to assist him in the U.S. But even President Bush, speaking Tuesday at the White House, warned there will likely be more to follow.

"The coalition we put together has hauled in over 2,400 people and you can call it 2,401 now. And there's just a full scale manhunt on. And Padilla is where he needs to be,'' said Mr. Bush.

"We will run down every lead, every hint," he said. "We're in for a long struggle in this war on terror. And there are people that still want to harm America. ... As we run down these killers or would-be killers we'll let you know."

Much of what Padilla learned about dirty bombs he picked up off the Internet. And there's evidence, officials say, that he had no intention of following the footsteps of alleged shoe bomber Richard Reid and dying as a martyr in a suicide attack.

Meanwhile, an INS memo issued Thursday and obtained by CBS News directs agents at U.S. airports, borders, and ports to do: "A complete and thorough search of all baggage" carried by Yemeni travelers and make "An inventory of all effects." Only those carrying diplomatic passports are exempt.

The memo specifically orders agents to look for "...large sums of currency, thermos bottles, night vision goggles or devices." It warns, "under no circumstances will an inspecting officer open a thermos bottle."

CBS News Correspondent Bob Orr reports the order was given after a recent raid of an apartment housing a number of Yemeni nationals somewhere in the Northeast.

In other revelations, authorities said Padilla met repeatedly with top al Qaeda leaders after Sept. 11 to discuss a range of attack options including blowing up hotels and gas stations. The officials said Padilla traveled to Afghanistan and Pakistan several times after the Sept. 11 attacks on America to meet senior al Qaeda leader Abu Zubaydah for talks on plans for other types of attacks.

Zubaydah is the imprisoned al Qaeda operative who helped tip off U.S. authorities to Padilla's activities. Padilla had been held in Department of Justice custody since his May 8 arrest. On Monday he was transferred from New York City to military custody in Charleston, S.C.

Deputy Defense Secretary Paul Wolfowitz said Muhajir had not yet provided information to investigators.

"He clearly had associates and one of the things we want to ask him about is who those associates were and how we can track them down," Wolfowitz said on the CBS "Early Show" program.

Officials said there were likely other operatives still working on the plots, which were only in the planning stages when Muhajir was arrested.

More details of Padilla's background surfaced Tuesday. Padilla, 31, has been described by authorities as a former gang member who grew up in Chicago. He was convicted at 15 as a juvenile of aggravated battery, armed robbery and attempted armed robbery. A law enforcement official said he was in custody there between November 1985 and May 1988.

He later moved to South Florida, where he was convicted in 1991 in Sunrise on charges of aggravated assault and discharging a firearm, court records show. Padilla, who identified himself as Catholic when he was booked on those charges, served one year of supervised release, until Aug. 4, 1993.

Police in Sunrise, which is about an hour north of Miami, said Padilla had brandished a .38-caliber revolver at another driver during a traffic encounter and later fired a shot from his car. No one was injured.

While in the Broward County jail, Padilla was accused of battery on a jail officer and resisting without violence in January 1992. He pleaded guilty and spent 10 months behind bars.

At the time of his arrest, Padilla told police he had worked at a Holiday Inn setting up banquet rooms for two weeks. Records show he has "Jose'' tattooed on his right arm.

While working a $200-a-week job at the Hilton Inn in Sunrise in May 1990, Padilla filed a worker's compensation claim after sustaining ``miscellaneous injuries to multiple body parts,'' said Rebecca Ardley of the Florida Division of Workers Compensation.

Ardley said Padilla did not miss more than 7 days of work and did not receive any benefits from claim.