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The Justice Department lawyer overseeing the terrorism investigation told lawmakers Wednesday the government's detention of hundreds of people is necessary to combat "sleeper cells" of terrorists quietly waiting to strike.

Assistant Attorney General Mike Chertoff testified that the government was lucky enough to avert a millennium celebration terrorist attack on Los Angeles in December 1999 with the border arrest of Ahmed Ressam. But Americans need more than a happenstance thwarting of attacks, he said.

"We could continue this war and hope we get lucky as we did in the Ressam case," Chertoff told the Senate Judiciary Committee.

"Or we can pursue a comprehensive and systematic investigative approach that aggressively uses every available, legally permissible investigative technique to identify, disrupt and, if possible, incarcerate and deport sleepers," he said.

Chertoff was greeted by pointed criticism from senators concerned the Bush administration had decided to use military tribunals to try some terrorist without first consulting with Congress.

"The administration has preferred to go it alone with no authorization or prior consultation with the legislative branch," Sen. Patrick Leahy, D-Vt., the committee chairman, lamented.

Chertoff defended the possible use of tribunals as well as the monitoring of jailhouse conversations between lawyers and suspects.

"Are we being aggressive and hard-nosed? You bet," Chertoff said. "In the aftermath of Sept. 11, how could we not be?"

Chertoff said only 16 prisoners' conversations with lawyers were being monitored by the government— 12 convicted terrorists and four people held on espionage charges. He said none was being held in connection with the Sept. 11 investigation.

Chertoff's comments came one day after his boss, Attorney General John Ashcroft gave the most thorough public accounting of terrorism arrests so far, naming for the first time nearly all of the 104 people who have been charged with federal crimes.

Ashcroft declined, however, to identify the hundreds of people being held on immigration violations, suggesting some were members of Osama bin Laden's al-Qaida network.

"I am not interested in providing, when we are at war, a list to Osama bin Laden and the al-Qaida network of the people we have detained that would make any easier their effort to kill Americans," the attorney general said.

On another front, law enforcement officials said Wednesday the FBI has asked a team of agents who specialize in looking for new leads in stumped cases to examine anthrax deaths in New York and Connecticut that have baffled authorities.

The team will re-examine evidence, the forensic and traditional investigative methods and the theories in the cases of Ottilie Lundgren, 94, of Oxford, Conn., and Kathy T. Nguyen, 61, of New York City.

There's no evidence either woman got the anthrax through the mail as in other known cases.

The agents are specially trained to "think outside the box" and look for clues that might be missed through normal investigation, the officials said.

In all, 603 people remain in detention, including a Palestinian with a kit to make box cutters and a Pakistani interested in hunting near a nuclear facility.

Others were held for alleged violations with no obvious connection to past or future attacks, according to documents reviewed by the AP.

Overseas, the investigation made progress with the arrest in Hamburg, Germany, of a man who held a bank account used by hijacker Marwan Al-Shehhi. Prosecutors identified the man as Mounir El M.

One of those detained, Mohdar Mohamed Abdoulah, a 23-year-old San Diego college student from Yemen, originally was held as a material witness, meaning he might have information important to the investigation. He was arrested and taken to New York City for grand jury testimony about his acquaintance with a Sept. 11 hijacker.

Abdoulah was returned to San Diego and charged with immigration violations. While a federal magistrate has granted Abdoulah his release on $500,000 bail, he remains in custody because property pledged for bail money is still $125,000 short, said his lawyer, Kerry Steigerwalt.

Steigerwalt has his own problems in defending his client. "The evidence has not been totally revealed by prosecutors," he said. "I don't know the strength of the case."

The lawyer's job is further complicated because of a new Justice Department policy to monitor conversations between detainees and their lawyers.

"There is a camera position right above us recording our entire encounter," Steigerwalt said of his meetings with Abdoulah in the Metropolitan Correctional Center in San Diego. "This certainly has had a chilling effect on what we discussed."

Another case involves a Pakistani man who took video footage of the World Trade Center a few days before the Sept. 11 attacks. Raza Nasir Khan was accused by federal agents in Wilmington, Del., of being an illegal immigrant who possessed firearms, documents show.

A Bureau of Alcohol, Tobacco and Firearms affidavit also alleged the Pakistani man requested maps of a hunting area near a rural Salem County, N.J., nuclear power plant and had a handheld global positioning system device.

The magistrate who ordered Khan held said she didn't see any connection to terrorism. In fact, few of the hundreds of pages of supporting documents provided to Congress mentioned a connection with the Sept. 11 attacks.

In northern California, an Immigration and Naturalization Service affidavit alleged that Nabil Sarama, a Palestinian, made a false statement to obtain a permanent residency card. Sarama was arrested Sept. 16 in Orlando, Fla., after police found him near a pay phone that had been used to make bomb threats, the documents alleged.

A search of his suitcase, the affidavit said, turned up a kit capable of making between eight and 12 box cutters — like the weapons used by the Sept. 11 hijackers. He also had a California Department of Motor Vehicles identification card, a Georgia driver's license, four Florida identification cards and a Palestinian Authority passport.