The number of confirmed dead under the rubble of the World Trade Center leapt by the largest margin yet as workers continued their grim task Monday.

Using heavy equipment to move giant steel beams and gargantuan pieces of debris from the fallen Twin Towers, the workers came across clumps of bodies, raising the number of known dead from 314 to 344.

"We're finding a lot of stuff in there," said construction worker John Yannucci. "It's not a happy sight."

Officials have identified 289 of the bodies, while 5,219 people are listed as missing.

Several media reports, citing unnamed fire department and search officials, said the bodies of at least 12 — and possibly as many as 25 — firefighters were found in the ruins Monday. But officials in the mayor's office said they could not comment on the recovery of bodies until the families had been notified. Officially, 343 firefighters are missing or dead in the attack.

More mourning took place farther north, at Central Park, where 2,500 family members, friends and coworkers gathered at a memorial for employees of Cantor Fitzgerald. The bond firm lost about 700 employees in the attack.

Joan Kirwin's husband, Glenn Kirwin, 40, was a partner with the firm and died in the attacks. She and four others who lost their spouses addressed the crowd.

"On the morning of September 11th, my life, as well as all of yours, changed forever," she said.

The victims' relatives and friends hugged and cried along with the speakers, who included the firm's chief executive, Howard Lutnick, and Mayor Rudolph Giuliani.

Giuliani said some would never completely heal from the wound of the terrorist attack.

"You'll need a great deal of support in getting through this. So will I, so will many, many people in New York City and around the globe," Giuliani said. "Your loss is shared by many, but particularly by a family of eight million people, and I speak for them when I say that your loved ones will never be forgotten."

Back at what has become known as Ground Zero, House Speaker Dennis Hastert, R-Ill., toured the wracked buildings with 108 other members of Congress. He said no one can know how much the recovery effort will cost.

"We don't know if that's the iceberg or the tip of the iceberg," Hastert said.

In a preliminary estimate last week, Senate aides said it would cost about $39 billion to clean up from the Sept. 11 attack and rebuild the city. Washington has pledged at least $20 billion. Some of the debris removal costs will be paid by $1 billion in bonds offered by New York City Monday. The short-term bonds will help with the recovery costs, including unemployment insurance for workers displaced by the attack.

But the damage reached far beyond Manhattan.

National Guard troops will be patrolling 19 airports around New York state beginning Friday. The 309 armed troops were called up by Gov. George Pataki as part of a nationwide deployment requested by President Bush to provide more security and coax travelers back to flying. More than half of the troops will be assigned to John F. Kennedy and LaGuardia airports in New York City.

Their presence "could go on for as along as six months," Pataki said.

In Albany, a study released Monday by state Assembly Democrats estimated that more than 7 percent of the state's private sector jobs, accounting for nearly 15 percent of the state's private sector wages, were threatened or eliminated by the Sept. 11 terrorist attack.

On Wednesday, President Bush was expected to make his second trip to New York City since the attack, probably making a visit to a school.

The director of the Federal Emergency Management Agency, Joe Allbaugh, said he also would be in New York City on Wednesday to visit the site.

Back at the debris field in lower Manhattan, iron worker Donnie Tuohy, 38, said the environment has shifted as most volunteers have been replaced by professional laborers, crane operators and iron workers.

"It's a different mood," he said. "Before, we thought we might find someone alive, but now that seems pretty hopeless."

The Associated Press contributed to this report.