Flight recorders found in Pentagon rubble

Smoke billows from the Pentagon after Tuesday's attack.

WASHINGTON (CNN) -- Both the flight data and cockpit voice recorders were recovered early Friday morning from the wreckage of American Airlines Flight 77, the hijacked jet that slammed into the Pentagon on Tuesday.

Also early Friday, members of the U.S. Coast Guard boarded a Carnival Cruise Line ship off the coast of Miami and detained two people who authorities determined have a "history of hijacking."

Investigators hope the so-called "black boxes" will shed light on what happened aboard the Boeing 757 after its takeoff from Washington's Dulles International Airport until the fiery crash a half hour after two other hijacked jets hit the twin towers of New York's World Trade Center.

"It's a significant development, and we are moving ahead," said Arlington County, Virginia, spokesman Dick Bridges.

A fourth plane crashed into a field in southwestern Pennsylvania. Searchers there have located the plane's flight data recorder.

In Miami, a law enforcement source said the ship was boarded by authorities in the early morning hours after the passenger list was checked by authorities, who identified the pair.

The Coast Guard said that at the request of Carnival Cruise Lines, the Immigration and Naturalization Service, the FBI, and Coast Guard officials boarded the Carnival Cruise ship "Fascination" at 3:15 a.m.

They assisted Carnival security personnel in detaining two individuals prior to ship's arrival later at the Port of Miami. At 6:52 a.m., they turned over the individuals to INS officials.

U.S. authorities said Thursday they believe they have identified most of the hijackers responsible for Tuesday's terrorist attacks; investigators cast an international net for accomplices, believed to be "a significant number."

FBI Director Robert Mueller said a preliminary investigation indicated 18 hijackers were on the four planes -- five on each of the two planes that crashed into the World Trade Center, and four each on the planes that crashed into the Pentagon and in Pennsylvania.

The widening investigation stretched from the Canadian border to Florida, from Pennsylvania into Europe, as U.S. investigators enlisted the help of the international law enforcement community.

U.S. Attorney General John Ashcroft said a team of 4,000 special agents at the FBI, joined by 3,000 support personnel, are working on the largest investigation in U.S. history.

Thousands perished when two hijacked commercial jets slammed into the World Trade Center's twin towers Tuesday morning, causing the 110-story towers to collapse in a terrifying cascade of cement, metal, glass and human bodies. A third jet slammed into the Pentagon, and a fourth crashed in rural Pennsylvania.

Among other developments:

-- Ashcroft said the pilots who hijacked the four planes were trained in the United States and had ground support.

-- U.S. Secretary of State Colin Powell indicated that suspected terrorist mastermind Osama bin Laden was among the primary suspects in the hijackings and crashes.

-- Investigators leading the probe of the Pennsylvania jetliner crash said they found debris six miles away from the crash site.

-- German police detained a male airport worker and brought in a woman for questioning in connection with the investigation.

-- A man who had initially been linked by U.S. authorities to Tuesday's terrorist attacks was cooperating with the FBI after his attorney said his identification had been stolen.

No arrests have been made in connection with the deadly hijackings, and no suspects have been identified by law enforcement authorities. An unspecified number of people have been detained for violations related to their immigration status.

Most of the people involved in the attacks have been accounted for, including those killed in the suicide attacks, but as many as 10 remain at large, sources said.

Some of those involved in the plot left suicide notes, but they are not believed to have been the hijackers, a government source told The Associated Press. It was unclear whether those who left the notes actually killed themselves.

Hijackers trained in U.S., Ashcroft says

Law enforcement sources said the hijackers had ties to the Middle East and bin Laden. Investigators said, however, that the probe is complicated by the fact that the hijackers died with their victims.

Speaking to CNN Thursday, Ashcroft echoed President Bush in calling the disasters "acts of war" and vowed to find the perpetrators.

"I'm not able to identify any one responsible party for you today," Ashcroft said. "I would say that we are making progress in this investigation and following and developing an understanding of the kinds of associations that the individuals who perpetrated these acts of war had."

"Between three and six individuals on each of the hijacked airplanes were involved," Ashcroft said. "We know that they were trained and technically proficient, that they were trained in the United States to fly, some of them at least, to fly these airplanes, and they flew them with deadly accuracy."

Ashcroft said that as of Thursday morning the U.S. government had received 2,055 tips through a hot line number and more than 22,700 tips on a Web site dedicated to the investigation. The hot line number is 1-866-483-5137.

New debris site in Pennsylvania

Investigators searching the wreckage of United Flight 93 in western Pennsylvania on Thursday found the plane's flight data recorder, said FBI spokesman Bill Crowley. The recorder was being sent to the National Transportation Safety Board in Washington for analysis.

"We are hoping that it will have some information that is pertinent to what occurred in the plane prior to its crashing," Crowley said.

The NTSB said United Airlines Flight 93 was heading eastward when it crashed in Somerset County.

FBI officials leading the investigation said it could take weeks to recover everything from the crash site. Crowley said archaeologists have been brought in to search the impact crater, which has been covered by a layer of dust.

Authorities also said another debris site had been cordoned off six to eight miles away from the original crash debris site. But Crowley said the debris was "very light material such as paper and thin nylon -- things that in the air with the wind would easily blow."

People questioned in Florida, Boston

The FBI questioned individuals in Boston, Massachusetts -- where two of the hijacked flights originated -- and Florida, where some of the suspected hijackers had apparently lived and attended flight schools.

In Boston, agents detained three men Wednesday for questioning but released them later in the day.

In Florida, more than 400 federal agents were put on the investigation. Several men were being investigated as suspects in the terrorist attacks after searching homes and rental car documents and poring over flight school student records across the state.

In Vero Beach, FBI agents searched four homes in three neighborhoods, according to witnesses.

A tenant in one of those houses, Adnan Bukhari, was cooperating with the federal agents, sources said.

Bukhari's brother, Ameer Bukhari, died in a small plane crash in Florida last year, according to a lawyer for the family.

Federal sources had initially identified the brothers as possible hijackers who had boarded one of the planes that originated in Boston. Their names had been tied to a car found at an airport in Portland, Maine. But Bukhari's attorney said it appeared their identifications were stolen and said Bukhari had no role in the hijackings.

Germans detain two in Hamburg

In Germany, that nation's top prosecutor said three of the suspected hijackers were of Arab descent and are believed to have lived in Hamburg, where they were members of an alleged terrorist cell.

Osama bin Laden

German police detained a male airport worker and brought in a woman for questioning in connection with the prosecutor's investigation into the attacks.

Multiple cells of terrorist groups participated in the operation, and the hijackers had possible ties to countries that included Saudi Arabia and Egypt, The Associated Press reported, citing law enforcement officials who spoke on condition of anonymity.

Officials said authorities were gathering evidence that the terrorist cells may have had prior involvement in earlier plots against the United States and may have been involved with bin Laden.