Despite a gagging order by the judge on hundreds of pages of phone taps, reporters have been obtaining a steady stream of transcripts, each one more embarrassing to the investigators than the last. The tapes were made with the help of the FBI's key informer, Emad Salem, a former Egyptian army commando who infiltrated the group of Muslims charged with the bombing that killed six people and injured more than 1,000 on 26 February.
In the latest leak federal agents allowed Mr Salem last May to buy a timing device for a bomb to make his undercover work more credible. Then they stole it back from the group's garage hideout and then, reconsidering the plight of their informer, put the device back in the garage. Or so the tapes say.
This particular farce unfolds in a series of conversations, taped in May, between Mr Emad and his FBI minders as the government investigation into the Trade Center blast extended into a second plot to blow up the United Nations, the Holland Tunnel and other New York landmarks.
The FBI agent is identified only as John. He tells Mr Salem: 'All right, there are two sides to this, Emad, but . . . the law says that we cannot allow that timer to be out of control, ok?' John says it is one thing to 'think Middle East', as Mr Salem has been urging the agents to do, but then adds: 'We have to think American, you also have to be concerned about that location being burglarised . . . nothing is safe today.'
'You finished?' interrupts Mr Salem. 'Can I talk?' He argues that he bought the timer for dollars 18 (pounds 12) in Manhattan's Chinatown on the instructions of Siddig Ibrahim Siddig Ali, a Sudanese later charged as ringleader of the second, thwarted, bomb plot.
It was the same shop, Mr Salem says, where he bought a timer for what was to become the Trade Center bomb, but he threw the device away after he and the FBI had a tiff, apparently over money.
According to reports, he will receive up to dollars 500,000 for his work on the Trade Center bombing and for his key role in unearthing the second plot for which another group, allegedly led by Sheik Omar Abdel-Rahman, the blind Egyptian cleric, is held responsible. Mr Abdel-Rahman is awaiting trial.
None of these tapes has yet been introduced as evidence in court where the prosecution has been concentrating on the task of identifying the scattered parts of the rented van it says was used to carry the bomb into the basement of the Trade Center, the world's second tallest building. There are no witnesses who saw any of the four defendants planting the bomb, or in the vicinity of the Trade Center. The prosecution's case is almost entirely built on circumstantial evidence.
The serial number on one of the van's engine parts apparently led the FBI to Mohammed Salameh, a Jordanian who rented the van in New Jersey. He claims the van was stolen the day before the bomb blast. Others charged with him are Mahmud Abouhalima, an Egyptian and Afghan war veteran named as the mastermind of the Trade Center bomb, Nidal Ayyad, a chemical engineer, who is charged with ordering the chemicals for the bomb, and Ahmad Ajaj, who is accused of entering the US last year with a false passport, bomb making manuals and materials. Two other defandants named in the case are still on the run.
Exactly how the investigators traced the others, after finding Mr Salameh, could be crucial for the defence, which argues that the government built its case to fit a predetermined theory and may have entrapped some of the defendants.
Parts of the tapes already revealed in the media suggest the investigation was not as originally portrayed - that it did not result solely from the identification of the van and then of Mr Salameh. The tapes even suggest that the FBI may have known of the bombing before it happened from Mr Salem. 'Did the FBI Blow It?' asked one headline.
In one FBI tape an agent says to Mr Salem: 'When they pushed this before, the information they had about this is that nothing was done about it . . . if it had been handled correctly we should have been . . .'
'Yeah,' Mr Salem interrupts.
'Able to intervene,' the agent says.