"He's been identified by senior members of the al Qaeda organization as a very, very, very serious threat to the United States interests both here and abroad," said Hector Pesquera, head of the FBI's South Florida office.
As CBS News Correspondent Jim Stewart reports, the FBI has upped the ante again in their search for El-Shukrijumah and he is now considered one of the top five terrorist threats to the United States.
El-Shukrijumah is an associate of Ramzi Binalshibh, Jose Padilla and Khalid Shaikh Mohammed. He trained in explosives at al Qaeda camps, according to the FBI, and is now poised to lead a terrorist cell in new attacks here.
"We think he's a big deal. We're concerned because of the time that he spent in the United States, because of his ability to get around the United States, because of his ability to speak the English language," says Pat D'Amuro Executive Assistant Director of the FBI's Counterterrorism unit.
Recent chatter among surviving al Qaeda members suggest El-Shukrijumah is seeking "soft" targets like apartment buildings and fuel tankers.
The FBI also has begun interviewing Iraqis in this country. Since the start of the war, agents have interviewed some 5,000 Iraqis now living in the U.S.
Shukrijumah's name first surfaced during the FBI's investigation of Sept. 11. Sources say it popped up again recently in a document recovered in Afghanistan and during the interrogation of al Qaeda kingpin Khalid Sheikh Mohammed.
His father, who lives near Miami, says El-Shukrijumah left Florida about three years ago. The last time the family heard from him, he was working as a computer engineer in Morocco.
"He's not a threat to anybody here in the U.S. because he's definitely not here in the U.S," said Nabil El-Shukrijumah, the brother of the suspected terrorist.
Though it is unusual for the FBI to issue this type of alert for someone who has not been charged, Steve Pomerantz, former chief of counterterrorism for the FBI, said that it demonstrates the seriousness of the situation.
"I think this is someone there are very, very concerned about, and want to find as quickly as they possibly can," he said.
The FBI says El-Shukrijumah was a friend of the Pakistani convicted last year of planning to bomb Florida power plants and a National Guard armory. And his apparent association with multiple al Qaeda figures makes him a likely threat. The FBI says it's received about 200 tips since issuing the alert for El-Shukrijumah.
"Law enforcement in this country operates entirely with the help of the public," Pomerantz said. "I mean, that's the premise of law enforcement in this country. We can't possibly be successful without the active cooperation of the public,"
The Iraqi interrogations, he said, are important for several reasons. "One is, these are people who are going to be obviously familiar with Iraq. And information that they would be willing to provide could be helpful in the current military campaign. So that's one aspect.
"And again, I think realistically you have to be somewhat concerned about who's here from Iraq. Are there people who are involved with terrorists, or who are supporters of terrorists? Historically, going back prior to Sept. 11, we have not been very careful about who we allowed in our country. And now we're playing catch-up to some extent to determine who's here. So that's another reason.
"And the third reason is, there's certainly the potential for there to be acts of violence, and hate crimes against people in the Arab and Islamic community. And by going out and alerting them to that potential, we enlist their help that way, too. So there are multiple reasons for conducting these interviews. And I think it's certainly justified and warranted in a time of war," Pomerantz explained.
Although the FBI says it is not using the interviews to arrest large numbers of Iraqis, two law enforcement officials speaking on condition of anonymity said about 30 people have been detained on immigration charges since the program began last week.
Late last month, Attorney General John Ashcroft gave the FBI and U.S. marshals authority to arrest people on immigration charges.
Some of those held are people the FBI had under surveillance and decided to apprehend when hostilities with Iraq began, the officials said. None had been charged with any terrorist plot, espionage or any other criminal offenses, the officials said.
By the end of this week, the FBI figures to complete its initial plan to interview 11,000 Iraqis living in the United States. These people were selected for immediate attention from a larger list of about 50,000 because they had recently traveled to Iraq or had ties to the Iraqi military, officials said.
The interviews are expected to continue at a slower pace after that priority group is finished. FBI officials say the interviews often provide them with new names that will require follow-up.
The interviews have received a mixed reception from Muslim communities around the country. Many people say they want to help the United States in its campaign against the Iraqi regime of Saddam Hussein but are concerned about being singled out for scrutiny.
"You don't have to be mistreated to be intimidated," said Ibrahim Hooper, spokesman for the Council on American-Islamic Relations. "If the FBI shows up at your place of work or talks to your neighbors, that's very intimidating."