Far-fetched conspiracy theories are common here, but there's a particularly insidious story spreading so widely among some Pakistanis now that it may fundamentally distort their view of what happened on Sept. 11.

The theory — which lacks a shred of evidence — goes like this: The attacks were actually carried out by the Israeli government, in an effort to both defame Islam and strike a secret blow against Christianity. The claim is that some 4,000 Jews who worked in the World Trade Center were told to either skip the day or show up late, thus saving them from the destruction that followed.

Americans recognize the story as a particularly cruel one, of course, since hundreds of Jews perished in the Twin Towers, along with an estimated 100 Israeli citizens. And many responsible Pakistanis dismiss the reports.

But that hasn't stopped a wide range of others from spreading the tale — with an alarming degree of detail and consistency.

"Ask yourself why more than 4,000 Jews working at the Twin Towers didn't go to work on the day of the attack," proclaimed a "fact sheet" issued by an Islamic student group that gathered outside the U.N. offices in a protest on Friday. "Either the Mossad did it and warned the Jews some time before, or the Jews ... warned the other Jews but did not warn the Americans."

Similar rallies around the capital in recent days have sounded the common theme that the U.S. investigation should be directed at Israel rather than Usama bin Laden.

"All Pakistani newspapers, all the papers in the area, they all write it here," shouted a protester at one rally, jabbing copies of articles proclaiming Israel's guilt, but offering no evidence. "They could not be wrong. They could not be wrong."

Several Pakistani media experts said the disinformation plan would not have much effect on the government's pro-U.S. policy. But that could change, said one leading newspaper editor, if the size of public protests grew dramatically. That has yet to happen.

Most such theories quickly pass through the usual circles of conspiracy enthusiasts and mutate into even more unbelievable tales before dissolving into the background of hyperbole. And that may happen here.

But this story has been told so often, by so many people, that it is simply taken as fact — no matter how wild it really is.

"I know every Jew working in the World Trade Center personally received a phone call to warn them," insisted Rashid, a restaurant worker. He dismissed a reporter's suggestions it would be quite impossible for such a large group of any workers to receive the calls without telling their bosses, co-workers and loved ones, or the police.

Even those who rightly dismiss the story acknowledge that its discussion has been widespread.

"It's certainly the talk of town, you can say that," said Dawnnewspaper editor Ahmed Kamel. "But there is no source on these stories. There has been no proof issued to support such claims."

But that hasn't stopped several newspapers from pumping the story. References to the "4,000 Jews" runs in news articles, columns and reader e-mails, often without refutation.

Kamel and some others believe the story was manufactured somewhere in the Middle East, and exported here through any number of extremist Islamic groups. There's no way to know. Many also blame the area's imams for spreading the story over and over again at the city's mosques.

It's not just extremist Muslims who believe the story. Many Pakistani professionals have implored journalists to investigate the claims, directing them to the FBI, the CIA, or any one of a number of U.S. federal agencies said to be looking into the charges.

There is no such investigation, U.S. officials insist. The evidence focuses clearly on bin Laden, a fact that will become clear when and if the Bush administration chooses to make that information public, they say.

For now, the conspiracy theorists have no explanation of why and how the suspects named by the Justice Department were on those fateful flights that morning. They either dismiss the claims, or argue that perhaps the suspects were actually Israeli agents.

They also cite the Bush administration's steady dedication to a prolonged and far-reaching investigation as "proof" of Israel's involvement.

"If it was really Usama, they would have finished this in one or two days," said Rashid. "They know it was the Jews, so they are just distracting us by all this other business."