US Attorney General Mr John Ashcroft said today some of the people responsible for the devastating September 11th attacks on the United States were likely still in the country planning more assaults.
Mr Ashcroft said law enforcement agencies nationwide were tracking down leads in an effort to find about 200 suspects and prevent additional strikes.
"I believe that it is very unlikely that all of those individuals who were associated with or involved with the terrorism events of September 11 and other terrorism events that may have been prepositioned and preplanned have been apprehended", Mr Ashcroft told NBC's Meet the Press.
"We are doing everything possible to disrupt, interrupt, prevent, to destabilize any additional activity", Mr Ashcroft said. "We are looking for individuals and aggressively pursuing them".
The prevailing theory that FBI agents are examining is that Osama bin Laden, who the United States views as the chief suspect in the attacks, was trying to activate more terror cells hiding in the United States, Newsweekreported.
The magazine said it had learned that the FBI has evidence from technical sources that Al Qaeda leaders in Afghanistan have placed at least four calls to telephone numbers in the United States since September 11th.
Three days after the FBI issued a warning there could soon be more attacks, Mr Ashcroft said the Justice Department remains on highest alert and again called on the public to report to law enforcement suspicious activities.