An effort to prosecute the self-proclaimed mastermind of the Sept. 11 terrorist attack and four co-defendants veered off track again Thursday as a pretrial hearing ended with new obstacles that threaten to further derail the case before a military tribunal at Guantanamo Bay.

Teams of lawyers managed barely four hours of court time over four days at the U.S. base in Cuba, bogged down by the potential legal implications of an apparent FBI investigation of the defense.