WASHINGTON (AP) _ Twenty-five people have been arrested for immigration violations as part of the investigation into Tuesday's terrorist attacks, a government official said Saturday.
None has been formally charged, either on immigration counts or with crimes relating to the four hijackings, said the official, speaking on condition of anonymity. FBI agents have interviewed many of those in Immigration and Naturalization Service custody and some of the detainees are cooperating, the official said.
Among the 25 are two men detained at an Amtrak station in Fort Worth, Texas, who were interviewed by FBI agents, taken into custody and then flown to New York.
They were removed from an Amtrak train during a routine drug search Wednesday night. Although no drugs were found, the men had box-cutting knives, authorities said, and also carried about $5,000 in cash, according to a federal official who spoke on condition of anonymity.
Hijackers in Tuesday's attacks used knives and box cutters to take control of the airliners.
Attorney General John Ashcroft said Saturday that the investigation into the terrorist attacks was ``developing a kind of clarity.''
``We are beginning to understand the ways in which this terrible crime was committed,'' said Ashcroft, who joined President Bush and administration officials at Camp David.
The first big break in the investigation came Friday when a man was arrested in New York in connection with this week's four airplane hijackings.
He was being held on a material witness warrant, said Jim Margolin, spokesman for the FBI in New York. The warrant allows authorities to hold someone considered crucial to the investigation without charging him with any crime. The man's identity was withheld.
A law enforcement source, speaking privately, said the man arrested was the same person detained Thursday at John F. Kennedy International Airport after showing what authorities said Friday was a pilot's license issued to his brother.
Both Margolin and New York Police Commissioner Bernard Kerik refused to provide any further details on the arrest. Court records were sealed.
Some of the 25 who have been arrested because they were discovered to have immigration problems when FBI agents questioned them about the case. Others were arrested as part of unrelated investigations and came to the attention of authorities investigating the hijackings.
Officials declined to say where the 25 were arrested or where they are being detained.
Late Friday, searchers recovered the cockpit voice recorder for United Flight 93, which crashed in southwestern Pennsylvania. It was not immediately clear what kind of shape the box was in. The box will be sent to the National Transportation Safety Board for analysis.
In Germany, police found ``airplane-related documents'' in a suitcase they believe belonged to one of the hijackers, federal investigators said Saturday.
Police seized the evidence late Friday in the industrial western city of Bochum when they searched the apartment of the girlfriend of Ziad Jarrah, who was aboard the plane that crashed in Pennsylvania, German authorities said.
Jarrah, a 26-year-old Lebanese native, often visited Bochum but lived and studied in Hamburg along with two others named by the United States as hijackers in Tuesday's attack, said Kay Nehm, German federal prosecutor said.
Federal investigators say Jarrah and the two others were part of an organization formed in Hamburg this year to destroy symbolic U.S. targets.
Pilot training is a central theme of the massive investigation into Tuesday's attacks. Several of the 19 hijackers whose names were released by the FBI Friday were pilots and had gone to aviation schools in Florida.
Among the 19 was Mohamed Atta of Hollywood and Coral Springs, Fla., identified by German authorities as being tied to an Islamic fundamentalist group that planned attacks on American targets.
Atta received pilot training at Huffman Aviation in Venice, Fla., and took two three-hour courses at SimCenter Inc. in Opa Locka, Fla., where he trained on a Boeing 727 full-motion flight simulator.
Besides Atta, the hijackers who were believed to be pilots included Hani Hajour, who was on the flight that crashed into the Pentagon; Wail Alshehri and Abdulaziz Alomari, who were on one of the Boston flights; Marwan Al-Shehhi, hijacking on United Flight 175 out of Boston and Ziad Jarrahi, who flew on United Flight 93 out of Newark, N.J., which crashed in a field 80 miles from Pittsburgh.
``The fact that there were a number of individuals that happened to have received training at flight schools here is news, quite obviously,'' said FBI Director Robert Mueller.
``If we had understood that to be the case, we would have, perhaps one could have, averted this,'' he said.
Officials said the men who were arrested in Texas had boarded a flight from Newark to San Antonio on Tuesday, the same morning of the attacks. The flight was diverted to St. Louis, where the men took an Amtrak train bound for San Antonio, an FBI spokeswoman said.
The Tarrant County, Texas, Sheriff's Office identified the men as Ayub Ali Khan, 51, and Mohammed Jaweed Azmath, 47. According to authorities, the men said they were from India.
Authorities also were looking for a Muslim cleric who previously was questioned by prosecutors in the 1998 embassy bombings case linked to Osama bin Laden, a Saudi extremist suspected of sponsoring a worldwide terrorist network.
The cleric, Moataz Al-Hallak, left the Northeast on Monday, the day before the attacks, and traveled to Texas, according to authorities and his lawyer.