The FBI issued an extraordinary terrorist alert Monday night, asking law enforcement and the American public to be on the lookout for a Yemeni man and several associates who might be plotting a terrorist attack as early as Tuesday.

The FBI scrambled to put the warning out after information emerged that one or more people were involved. Officials said the intelligence, while deemed credible, was not specific about possible targets.

The alert identified one possible attacker as Fawaz Yahya al-Rabeei, a Yemeni national born in Saudi Arabia in 1979. It listed about a dozen associates of al-Rabeei, most from Saudi Arabia and Yemen. One associate was listed as possibly coming from Tunisia.

The bureau at mid-evening posted the alert on its public Web site, www.fbi.gov, to help Americans identify the possible perpetrators. The Associated Press obtained the initial alert from government sources.

"Recent information indicates a planned attack may occur in the United States or against U.S. interests on or around Feb. 12, 2002. One or more operatives may be involved in the attack," the alert to 18,000 law enforcement agencies said.

The alert asked police "to stop and detain" any of the named individuals in alert and that all "should be considered extremely dangerous."

Although the alert was issued on the fourth night of the Winter Olympics in Salt Lake City, officials said there was no intelligence suggesting the games were a possible target. Instead, they urged that all locations in the United States and abroad with Americans to be on guard.

Law enforcement officials said there was no evidence that al-Rabeei had entered the United States. The alert did not say whether the attack was planned by or involved Osama bin Laden's al-Qaida network.

The FBI's alert indicated the information came from interviews of detainees in Afghanistan and Guantanamo Bay, Cuba, where several al-Qaida operatives are being held along with Taliban fighters.

Officials said the information was specific enough to be deemed credible but had come in so recently that it could not be corroborated yet. The warning was nonetheless issued out of an abundance of caution and because Tuesday was near, they said.

Before Monday, FBI and Homeland Security officials had issued three general alerts urging all Americans to be cautious and on the lookout for possible terrorist activities.

The last was issued Dec. 3 and was supposed to last through the holidays. It has since been extended through the Winter Olympics in Salt Lake City and is supposed to expire around March 11.

In addition, the FBI has issued numerous narrower alerts to specific industries when uncorroborated information about threats to their facilities emerges. In the last month, such alerts went to nuclear power plant operators and to operators of Internet sites cautioning about possible threats.

Often times, FBI officials later conclude the information that prompted such alerts is not credible or could not be corroborated.

On some occasions, local law enforcement officials have complained they learned from news media about the warnings before they saw the alerts over the FBI communications system.

Monday's warning was carefully organized to ensure that police, news media and the public learned about them at the same time, officials said.

(Copyright 2002 by The Associated Press. All Rights Reserved.)