U.S. authorities have disrupted at least four attempted terrorist attacks against U.S. facilities overseas in the five weeks since Sept. 11, a government official confirmed Monday.

European police have arrested dozens of suspected terrorists and their associates since last month's hijackings. The foiling of the four attacks is one of the few tangible accomplishments of a sprawling, secretive investigation that has detained about 700 people in the United States and swept across the globe, but has not resulted in any criminal charges directly related to the hijackings.

U.S. officials have repeatedly said the main goal of the investigation is to prevent further deadly assaults, rather than simply to build an airtight legal case against those responsible for the Sept. 11 hijackings.

The revelation of the four attempted attacks meshed with recent government warnings about ongoing threats against Americans. Last Thursday, the FBI warned that "there may be additional attacks within the United States and against U.S. interests overseas over the next several days."

As the domestic investigation continued Monday, eight men of Egyptian origin from the area of Evansville, Ind., were being held in federal custody. They were detained on material witness warrants issued by a federal grand jury in Alexandria, Va., and were expected to be transported there.

Officials declined to name all the intended targets of the four overseas plots. But they said one involved a planned assault on the U.S. Embassy in Paris, and British news reports described a disrupted attack against a NATO site in Brussels.

The other two foiled plots involved a U.S. Embassy building in Yemen and an American facility in Turkey, according to The Associated Press.

Francis Taylor, the State Department's counter-terrorism chief, confirmed that attacks have been prevented but refused to give details. "Our efforts are focused on preventing terrorists from conducting their operations," Taylor said at a news conference. "We've had some success and hope to have many more in the future."

Justice Department officials declined to comment on the report.

"It's very difficult to know if you've prevented an attack," one law enforcement official said. "All you can do is everything in your power. You may not know if you've been successful. You take it day by day. Obviously, our efforts are primarily at preventing another attack as opposed to prosecution."

U.S. Embassies and other sites had been targets long before Sept. 11, as the 1998 attacks against the embassies in Kenya and Tanzania show.

The best known of the disrupted attacks involved a plot to blow up the U.S. Embassy in France. Police in Paris on Sept. 20 rounded up seven suspected Islamic militants in that alleged conspiracy, and suspects also have been arrested in the Netherlands, Belgium and Spain.

Much of the information about the plan has come from an alleged member of Osama bin Laden's network, Djamel Beghal, who was arrested in late July in the United Arab Emirates.

According to the plan that Beghal reportedly revealed to investigators, Nizar Trabelsi, a Tunisian who was arrested Sept. 13 in Belgium, was to get inside the U.S. Embassy with explosives strapped to his body. At the same time, a mini-van packed with explosives was to explode outside the U.S. cultural center in Paris.

The only known connection between Turkey and the current terrorism investigation came when authorities searched a Detroit apartment on Sept. 17 and charged three men they found there with possession of false documents.

Among those documents was a day planner with notations in Arabic mentioning an "American base in Turkey." FBI agents had gone to the apartment in search of another man, Nabil Al-Marabh, who was later arrested in Burbank, Ill., a Chicago suburb.

But a law-enforcement official familiar with the Detroit arrests said a link has not been found to any terrorist plot in Turkey. One man detained as a result of the search, Farouk Ali-Haimoud, was released last week as prosecutors dropped the immigration-related charges against him.

Yemen is considered a relatively friendly haven for terrorists. That is where the USS Cole was bombed last year, and several Yemeni nationals have been recently charged with terrorist activity.

As the investigation continued in the United States, the FBI refused to comment about eight men who appeared Friday behind closed doors in a federal courtroom in Evansville. Miles Hart, administrator of the county jail in Henderson County, Ky., confirmed that federal marshals brought the men in Thursday night and they were taken to an undisclosed location Saturday.

The jail's chief deputy, Col. Ron Harrington, spoke with the U.S. marshals. "The only thing they said was that they were being investigated for alleged terrorist links," Harrington said. "That could mean anything."

U.S. Magistrate Judge William Hussmann Jr. said the men were being held as grand jury witnesses and cited the federal material witness statute when he closed the court hearing Friday, said Patrick Shoulders, a lawyer representing the Evansville Courier & Press.

Shoulders filed a motion on behalf of the newspaper to open the hearing, but Hussmann rejected that motion. Hussmann said the men were wanted on warrants issued by a federal grand jury in Alexandria, according to Shoulders.

One of the men, Tarek Albasti, owns the Crazy Tomato restaurant in Evansville. Several of the other detainees work there.

Mohammed Abutaqa, a friend of Albasti, said he did not believe the men had any information related to terrorist activities. He said he was upset the men were not permitted to speak with their families and were taken away in handcuffs.

Albasti had taken flying lessons, Abutaqa said, adding, "It's a hobby."

Meanwhile, officials continue to believe that terrorist cells may be active in the United States.

Vincent Cannistraro, a former CIA counter-terrorism chief who is in contact with the terrorism probe, said investigators think active members of al-Qaida remain in the United States.

Chicago Tribune staff reporters Cam Simpson and Sam Roe in Chicago contributed to this report