Officials in Guyana and Trinidad continue their search for the fourth suspect in the JFK airport terror plot uncovered Friday.
The suspect, Abdel Nur, from Guyana, reportedly left his home three weeks ago and headed for Trinidad and Tobago, where two other suspects are being held pending extradition.
Federal officials say the plot to blow up fuel lines at John F. Kennedy International Airport in New York was stopped long before the alleged terrorists were anywhere near being able to carry it out. That's partly because investigators say they had an informant inside the group.
ABC News terrorism analyst Jack Cloonan says that is incredibly important.
"It is the human element to it all," Cloonan says. "It is a good informant who can preempt and tell you everything that you have to know about this particular case."
That informant, a twice convicted drug dealer, was just part of a far-reaching effort by New York City police and the FBI to prepare against the threat of home-grown terrorism -- to combat angry Americans, inspired to attack their own country.
"It's a movement. It's a philosophy, " says New York City Police Commissioner Ray Kelly. "And they're motivated by the same hatred that motivates al Qaeda."
The alleged terrorists in the Kennedy Airport plot had no known ties to al Qaeda and one is an American citizen. So is one of the suspects behind the alleged plot against Fort Dix in New Jersey.
The FBI says this type of terrorist can be more difficult to track. So law enforcement officials are leaving no stone unturned when it comes to homegrown extremists, John Miller, the FBI's assistant director of public affairs, told ABC News' George Stephanopoulos on "This Week" Sunday -- a day after officials charged four men in the JFK plot.
"When you're looking at inspired-through-the-Internet, homegrown extremists, well, they can pop up anywhere," Miller said. "So now, instead of having a focus in a certain direction, you have to focus in a 360-degree radius every moment of every day."
That's just what law enforcement has been doing. ABC News has learned that for three years, New York City police have been going door-to-door in Muslim neighborhoods, introducing themselves to shopkeepers, community leaders, and imams -- 30,000 visits -- trying to overcome the suspicion many in ethnic neighborhoods feel toward the police.
"Police Commissioner Kelly shows very good character to listen to the minorities' problems ... and he's willing to communicate to Muslim communities," says Ahmed Jamil, president of the Dar al Dawah mosque in Queens, N.Y. "At the end of the day, we're all Americans. And the end of the day, we need the safety and the harmony of our community and our society."
Authorities in New York and in New Jersey, which also has a significant Muslim population, want to prevent the kind of isolation of ethnic neighborhoods that has led to the growth of homegrown terrorists in other countries.
In England, for example, the sons of immigrants are blamed for the 2005 subway bombings in London.
Investigators had been tracking the alleged JFK plotters since 2006. The suspects included a former cargo handler at JFK Airport and a former member of Guyana's parliament. The plan of attack was in its early stages, but the extremists had hopes of causing more harm to the United States than the events of 9/11.