NEW YORK (Reuters) – New York officials vowed on Saturday to keep hunting for survivors in half a million tons of twisted metal and debris from the devastated World Trade Center, though no one has been found alive in three days.

The number of missing after Tuesday’s attack climbed to 4,972, 255 more than estimated on Friday, Police Commissioner Bernard Kerik said. The remains of 152 have been recovered and 92 of those have been identified. Just five people have been pulled out alive, two on Tuesday and three on Wednesday.

Only a fraction of the 450,000 tons of rubble has been cleared and weary, overwhelmed rescuers are combing through all of it for survivors, bodies and body parts.

The landmark 110-story twin towers collapsed shortly after hijackers commandeered two commercial planes and crashed them into the symbol of American financial might.

“If you look at the site, there are a number of voids that could still exist. There are a number of areas, vacuum areas that could still exist,” Kerik said at a news conference.

“It’s possible that people could still be alive. We’re going to keep up hope, keep our prayers going and just hope for the best. It is possible. If you look at other disasters or tragedies around the world, people have been pulled out from these things five to six, seven days later and still alive. We’re not going to give up hope,” he said.

President Bush named Saudi-exile Osama bin Laden, who is sheltered by Afghanistan, as the prime suspect on Saturday in masterminding the worst attack on U.S. soil since the Japanese bombing of Pearl Harbor in 1941.

In apparently coordinated strikes, a third hijacked plane crashed into the Pentagon, U.S. military headquarters outside Washington, shortly after the towers were hit. A fourth hijacked plane crashed in rural Pennsylvania.

The president toured the devastation in New York on Friday, comforted relatives of victims and rallied exhausted rescuers. Rescue workers greeted his speech with chants of “USA! USA!”

FUNERALS FOR FIREFIGHTERS

Funerals were held on Saturday for New York Fire Department First Deputy Commissioner William Feehan, Chief of Department Peter Ganci and Department Chaplain Mychal Judge. The men were among 350 firefighters who were the first on the scene after the planes hit the towers and the first to die when the 1360-foot steel-and-glass columns collapsed.

Former President Bill Clinton, New York Sen. Hillary Clinton and their daughter Chelsea attended the funeral of Judge, who died of a heart attack while administering last rites to a dying fireman as towers came crashing down.

Sen. Clinton, addressing the mourners, said she knew Judge and hearing of his death made the attacks personal for her.

“It will take a very long time before any of us find the words to express what this cowardly, evil act meant and did to the people we loved and to our city and our country,” she said.

In addition to nearly 5,000 trade center office workers and firemen feared dead in New York, hundreds of passengers on the four hijacked planes perished and more than 100 Pentagon workers are also feared dead.

RESCUERS OVERWHELMED

Five days after strikes that stunned the world, gray and brown clouds still billowed from the rubble of what were once New York’s tallest buildings and a stench rose from the site.

“Everybody is overwhelmed,” said Bob Moody, a captain firefighter from Montgomery County, Maryland. “New York has suffered so much of a loss, you cannot imagine.

“You cannot appreciate the devastation and loss until you see it. We find bits and pieces of people. You keep hoping you’ll come across a miraculous save. We are hopeful but not expecting much,” he said.

In many cases, rescuers were only able to recover small body parts so family members of the missing were asked to bring hairbrushes, toothbrushes or clothing for DNA identification.

Technicians plan to scour the wreckage for signals from cellular phones and pagers in hopes they can help rescue crews zero in on any survivors, according to spokesman for the Federal Emergency Management Agency.

Although an active signal from a wireless device would not indicate that its owner survived the attack, it could help crews direct their efforts into air pockets and basement areas of the rubble where people may be huddled awaiting rescue.

OUTPOURING OF SUPPORT

One of the emblems of the attack in New York has become the thousands of family members wandering city streets with pictures and descriptions of the missing, hoping to track down clues to their fate. They have been scouring hospitals and lining up at centers that collect data on the missing.

In an outpouring of support, thousands of New Yorkers off work for the weekend formed long lines outside the Jacob K. Javits Convention Center in midtown Manhattan to volunteer in rescue efforts and help stricken families.

The city was overwhelmed by the offers and said it had more volunteers than it needed at this point. Officials distributed excess food and supplies to hospitals and homeless shelters.

“The generosity is extraordinary and I cannot tell you how much we appreciate it,” said First Deputy Mayor Joe Lohta.

About 400 construction workers were waiting since 7 a.m. EDT outside the Javits Center, many wearing dirty jeans with shovels slung over their shoulders and American flags sticking out of their hard hats.

“Something happened to me on Tuesday,” said Steve Rowan, a 49-year-old builder from Riverdale, New Jersey. “I wanted to be here ever since. I’m not looking for money. I’m willing to sweep, shovel whatever to do my part.”

Iron workers were in particular demand in rescue efforts.

“You want to pitch in and help like everyone else,” said Dan Kelly, a 44-year-old welder from Woodside, Queens.

A wave of patriotism was sweeping the city not known for its sentimentality.

The American flag was everywhere — on T-shirts and giant billboards of Times Square, sticking out of people’s back pockets, draped from windows, hanging off cranes, decorating hot-dog vending stands on street corners and flying from cars and Harley Davidson motorcycles.

Some New Yorkers, especially those living closest to the disaster area, have been wearing gas masks to filter the smoky, acrid air wafting from the smoldering ruins downtown.

STOCK EXCHANGE TO REOPEN

In preparation for Monday’s reopening of the New York stock exchanges, city authorities allowed limited access to the Wall Street financial district for the first time since the attack.

Mayor Rudolph Giuliani said the city would open a route to allow Wall Street traders to return to their offices.

The New York Stock Exchange, American Stock Exchange and the Nasdaq have been closed for four days — the longest shutdown since the outbreak of the First World War.

The NYSE and its member firms — banks and brokerages — were testing their systems over the weekend. The stock exchange is just a five-minute walk from where the twin towers once stood.

Business owners were beginning to dig out, washing windows and sweeping sidewalks as construction workers dug up the streets to repair pipes and electrical lines.

Speakers in a window of the Federal Reserve Bank of New York, near the disaster site, blared “America the Beautiful.”

Security was tight around the rescue operation to keep gawking crowds at bay.

Subway trains began rolling into the financial district for the first time since the attack on Saturday. Cars are still banned.

(Additional reporting by Eric Burroughs, Jon Herskovitz, Daniel Bases, Genevieve Wilkinson)