A second case of anthrax exposure drew FBI scrutiny in Florida, where a 63-year-old year-old man died of the disease last week. "It is the source of concern," said White House spokesman Ari Fleischer.

With American bombs dropping on targets overseas, Ashcroft outlined a long list of steps taken by the government to guard against the threat of further terrorist strikes, including stepped-up security at nuclear facilities and power plants. At the same time, former Pennsylvania Gov. Tom Ridge reported for duty as the first director of the Office of Homeland Security.

"Strikes are continuing as we speak," said Air Force Gen. Richard Myers, chairman of the Joint Chiefs of Staff. He said the fresh bombardment _ bombs delivered by 20 warplanes as well as cruise missiles launched from ships _ was accompanied by a renewed airdrop of humanitarian assistance.

Halfway around the world, anti-aircraft fire could be heard in the Afghan capital of Kabul, electricity was cut and Taliban radio told residents to close the blinds on their windows and remain indoors.

Other strikes were under way on the Taliban stronghold of Kandahar, according to a Taliban official who refused to be identified by name. In addition, Taliban positions around the northern city of Mazar-e-Sharif were under attack, a spokesman for the opposition northern alliance, Ashraf Nadim, said by telephone.

Monday's attack came almost precisely 24 hours after the opening of the conventional military campaign aimed at military targets and terrorist training camps run by Osama bin Laden, the man accused of masterminding the Sept. 11 attacks in New York and Washington that killed more than 5,000.

At the Pentagon, Defense Secretary Donald H. Rumsfeld suggested there was much left to do after the first night's assault. "We believe we've made progress toward eliminating the air defense sites," he said. "We believe we've made an impact on military airfields. ... We cannot yet state with certainty we have destroyed" dozens of command-and-control and other military targets," he said.

Rumsfeld also said: "There have been some ground forces targeted." He said they were principally in the northern part of Afghanistan. There, northern alliance forces launched an attack on Taliban troops on Sunday in a strike coordinated with the aerial bombardment.

In an indication the United States might want to some day expand the military operation, a senior administration official said formal notification had been sent to the U.N. Security Council that counterterrorism attacks may be extended beyond Afghanistan.

A legal document sent Sunday to the council reaffirmed the attack on the Taliban was an act of self-defense under the U.N. charter and said the United States reserves the right to strike at terrorist cells beyond the South Asian country, according to the official, who spoke on condition of anonymity.

In a prelude to the night's military attacks, Bush presided over a swearing-in ceremony for Ridge.

"On all efforts, on all fronts, we're going to be ongoing and relentless as we tighten the net of justice" against terrorists, said the commander in chief.

He added that the United States is working "to not only protect ourselves but to bring the evildoers to justice."

With the FBI cautioning persistently about the threat of renewed terrorism, officials were looking warily to southern Florida, where local health officials reported finding anthrax bacteria in the nasal passage of a co-worker of the man who died last week from the disease. The building where both worked was closed after the bacteria also were detected there.

In his comments, Ashcroft said authorities viewed the second case of anthrax exposure very seriously. He said the government had sealed the building where the two men worked. Without additional laboratory results and other investigative steps, he said, "We are unable to make a conclusive statement about the nature of this as either an attack or an occurrence" that is natural in origin.

President Bush was informed of the developments on Sunday night.

Bush spoke at the White House after British Defense Secretary Geoff Hoon said 30 sites had been hit in Sunday's opening wave of U.S.-led attacks, including the military infrastructure of Afghanistan's Taliban regime and the bases of bin Laden and his al-Qaida terror network.

Adm. Sir Michael Boyce, chief of the British defense staff, said some of the camps may have been empty. Still, he said, "There is certainly merit in denying those camps further use. And that is what we have done."

Earlier, Defense Secretary Donald H. Rumsfeld said all planes returned safely to their far-flung bases following the onset of military action designed to bring the battle to the terrorists responsible for the attacks that killed thousands in New York, Washington and Pennsylvania.

A senior defense official, speaking on condition of anonymity, said the next wave of attacks would hit again at the Taliban's military airfields, tanks and MiG fighters. The attack would use hunter-strike aircraft from naval ships in the region and fewer long-range bombers, the official said.

Before Sunday's attacks, the Taliban was believed to have about 15 operating fighter-bombers of Soviet vintage, and several hundred tanks and armored vehicles.

Ridge, who resigned as Pennsylvania governor a few days ago, took his seat at the center of power in Washington. "The size and scope of this challenge are immense," he said moments after he was sworn in. His job, he added, is to close the gaps in the nation's current anti-terrorism efforts _ gaps that permitted small cells of terrorists to kill thousands when they flew hijacked planes into high-visibility targets.

Vice President Dick Cheney had been slated to swear in Ridge. But he remained at an undisclosed secure location, and Supreme Court Justice Clarence Thomas filled in for him.

Bush, presiding, said Rumsfeld had informed him "that the military mission of yesterday was executed as planned and at the same time, that our good nation dropped over 37,000 kits of food and medicine."

As for the initial round of military targets, "We know they were successfully hit in many respects," Rumsfeld said. He told The Associated Press that the assault targeted two to three dozens sites, including terrorist training camps, military airfields, military aircraft, air defense radars and surface-to-air missile sites.

Rumsfeld rejected Taliban claims that they had shot down an aircraft, as well as claims of significant civilian casualties.

"We have approved every single target _ and each one is a military target," he told the AP.