WASHINGTON, May 28 - The F.B.I. issued an urgent bulletin to several cities on Friday that warned of the prospect of an imminent terrorist attack but retracted the alert hours later, after the intelligence proved unfounded, officials said.

The alert went to law enforcement officials in two or three cities to warn of intelligence that indicated the prospect of an attack in the next 24 hours, officials said. Officials would not give the names of the cities.
http://www.nytimes.com/2004/05/29/politics/29terror.html

A law enforcement official at another city, who insisted that he and the city not be named, said authorities there had received a call late in the day from the Federal Bureau of Investigation alerting them to the possibility of an "imminent" attack there. Later, however, the FBI called to withdraw the warning.

The official, citing recent questions about the credibility of the terrorist intelligence from the bureau, said, "It's getting harder and harder to defend them."