U.S. intelligence agencies have seen an increased level of activity suggesting another al Qaeda terrorist operation could be in the works, though they have received no specific information about a possible attack, government officials told CNN. "There has been an increased level of chatter and activity," said a senior administration official, who did not want to be identified. Another government official confirmed that the volume of communications among suspected al Qaeda operatives "has definitely picked up in the last month or so" and characterized them as "troubling" and having prompted a "heightened level of concern." The source added that both the volume and pattern of the communications were similar to those of messages intercepted in the months before the September 11 attacks.