Who produced the fake Niger papers? There is nothing approaching a consensus on this question within the intelligence community. There has been published speculation about the intelligence services of several different countries. One theory, favored by some journalists in Rome, is that sismi produced the false documents and passed them to Panorama for publication.

Another explanation was provided by a former senior C.I.A. officer. He had begun talking to me about the Niger papers in March, when I first wrote about the forgery, and said, “Somebody deliberately let something false get in there.” He became more forthcoming in subsequent months, eventually saying that a small group of disgruntled retired C.I.A. clandestine operators had banded together in the late summer of last year and drafted the fraudulent documents themselves.

“The agency guys were so pissed at Cheney,” the former officer said. “They said, ‘O.K, we’re going to put the bite on these guys.’” My source said that he was first told of the fabrication late last year, at one of the many holiday gatherings in the Washington area of past and present C.I.A. officials. “Everyone was bragging about it—‘Here’s what we did. It was cool, cool, cool.’” These retirees, he said, had superb contacts among current officers in the agency and were informed in detail of the sismi intelligence.

“They thought that, with this crowd, it was the only way to go—to nail these guys who were not practicing good tradecraft and vetting intelligence,” my source said. “They thought it’d be bought at lower levels—a big bluff.” The thinking, he said, was that the documents would be endorsed by Iraq hawks at the top of the Bush Administration, who would be unable to resist flaunting them at a press conference or an interagency government meeting. They would then look foolish when intelligence officials pointed out that they were obvious fakes. But the tactic backfired, he said, when the papers won widespread acceptance within the Administration. “It got out of control.”

Like all large institutions, C.I.A. headquarters, in Langley, Virginia, is full of water-cooler gossip, and a retired clandestine officer told me this summer that the story about a former operations officer faking the documents is making the rounds. “What’s telling,” he added, “is that the story, whether it’s true or not, is believed”—an extraordinary commentary on the level of mistrust, bitterness, and demoralization within the C.I.A. under the Bush Administration. (William Harlow, the C.I.A. spokesman, said that the agency had no more evidence that former members of the C.I.A. had forged the documents “than we have that they were forged by Mr. Hersh.”)

The F.B.I. has been investigating the forgery at the request of the Senate Intelligence Committee. A senior F.B.I. official told me that the possibility that the documents were falsified by someone inside the American intelligence community had not been ruled out. “This story could go several directions,” he said. “We haven’t gotten anything solid, and we’ve looked.” He said that the F.B.I. agents assigned to the case are putting a great deal of effort into the investigation. But “somebody’s hiding something, and they’re hiding it pretty well.”