WASHINGTON - The government raised the national threat level last week after U.S. intelligence obtained evidence that al-Qaida operatives may be positioning themselves to carry out two major attacks, including one in the United States, government officials said yesterday.
Officials said the intelligence is especially worrisome because it shows that the al-Qaida network may have gone beyond the planning stages for two distinct plots, one in America and a second in the Arabian peninsula, and may have dispatched low-level operatives to conduct logistical or operational work needed to carry them out.
Some U.S. intelligence officials said it is not clear from the fragmentary evidence they have obtained whether the activity among al-Qaida operatives involves preliminary work, such as the casing or surveillance of possible targets and logistical support for cells involved in plots, or is instead evidence of more advanced work on imminent attacks.
The intelligence suggesting that al-Qaida has moved from planning to operational activity was a factor in the government's decision last Friday to raise the color-coded national threat level from yellow to orange, officials said.
"One of the reasons taken into consideration in moving to orange was the concern that al-Qaida was moving from the planning stages to going operational," a Bush administration official said yesterday. "It is why we need to do more, to deploy more assets and physical barriers, because we are more concerned about the potential for attack."
The official added that intercepts of telephone conversations, e-mail messages and other intelligence indicating that terrorists have moved closer to an attack is one of the key considerations used by the new Homeland Security Department to determine when the threat level should be raised.
The evidence of activity among al-Qaida operatives also explains why in recent days CIA Director George J. Tenet and Robert S. Mueller III, the FBI director, have given explicit warnings about possible al-Qaida attacks in the United States and overseas.
But officials said the evidence obtained by U.S. intelligence is not detailed enough to point to specific targets, to individual operatives, to the exact timing of potential attacks or even to the methods or weapons to be used. It is still unclear whether the plots involve conventional weapons or weapons of mass destruction, such as chemical, biological or radiological devices. There have been some troubling indications, however, of al-Qaida's renewed efforts to obtain a device that spreads deadly radiation through conventional explosives, in order to cause mass casualties, U.S. officials have said in recent days.
After detecting indications of movement around the world by al-Qaida operatives and other signs of increased activity, U.S. intelligence officials are trying to identify the terrorist group's foot soldiers who may be involved in carrying out the latest plots and their whereabouts. Intelligence analysts believe that these low-level operatives may have received directions from high-ranking al-Qaida leaders, and may now be in the process of carrying out their orders, which makes prevention inside the United States such a high priority.
Officials said there are indications that Khalid Sheik Mohammed, one of the central planners of the Sept. 11 plot, might be involved in planning the current operations. But officials indicated that they are now most concerned with identifying and tracking lower-level al-Qaida operatives who may have been dispatched.
The intelligence indicates two distinct strands of activity among al-Qaida operatives, and U.S. analysts believe that means there may be two terrorist plots in the works, officials said. The intelligence is fragmentary, but the discussions among al-Qaida operatives of the movement of personnel and other activity seems to be going in two directions.
"They are seeing a lot of activity, and it doesn't all seem related to the same thing," said one official. "The evidence seems to break into two piles."
Much of the intelligence collected by the United States in recent weeks comes from intercepted communications among suspected al-Qaida operatives. Analysts began to see an increased level of communications recently, and some of those intercepts apparently refer to the movement of personnel and other signs of action.
But U.S. officials also said yesterday that the intelligence pointing to an imminent threat goes beyond the communications intercepts, although they declined to provide details. While they would not provide specifics, one key indicator used by counterterrorism officials to track al-Qaida's movements is to follow evidence of financial transactions among supporters of the terrorist network. The money trail can sometimes aid in tracking al-Qaida operatives.
One official said concerns within the intelligence community peaked Wednesday night, when "chatter" among al-Qaida operatives suddenly dropped off. The official said there were fears that the operatives, having moved into place, were quiet because they had finished their preparations and were poised for an attack.
Although government officials said they had no immediate plans to raise the threat level again, a jittery nation stayed on a high level of alert yesterday.
Officials at Dallas-Fort Worth International Airport evacuated three terminals and closed security checkpoints for about 90 minutes early yesterday after a fire door was spotted ajar.
In the suburbs of Atlanta, a high school was evacuated and classes canceled for the day after a device filled with blue liquid and with a timer attached was found in a hallway.
Federal agents in Florida arrested 32 employees at airports in Tampa, Orlando, Jacksonville and Sarasota on charges that they used false information to obtain security badges. Federal officials said there was no evidence linking any of the individuals to terrorism.
And the U.S. Customs Service announced it had refused to let 13 sea containers destined for U.S. ports, including Los Angeles and New York, be loaded on ships overseas because of insufficient information about their contents.