NEW YORK (AP) - Thousands of workers, stacked in skyscrapers, packed within walking distance of each other in lower Manhattan - it once was ideal for negotiating the world's financial business. But now, as giant cranes dip into the fallen World Trade Center nearby, some are wondering whether the very idea of a financial district concentrated downtown collapsed along with the twin towers.

Several major financial firms whose office space was damaged are moving to new quarters in midtown Manhattan, New Jersey and elsewhere, and many have given no indication of whether they will return to lower Manhattan once their buildings are repaired.

``The financial district is dispersed, post 9-11,'' said M. Myers Mermel, a former real estate adviser with Morgan Stanley who now runs TenantWise.com, an online commercial real-estate firm. ``The question remains whether it can be reassembled. Tenants are indicating that there is little enthusiasm for returning downtown.''

Technology is making it less compelling to return. Computers, teleconferencing and other electronic means of doing business have made it much less important for brokers and others to work within walking distance of each other in one concentrated area of skyscrapers.

``The days of exchanging papers and running the stock certificates around certainly are long gone,'' said John Cefaly, vice chairman of Cushman & Wakefield, one of downtown's major real estate firms. ``Do all functions need to be in the same location? I think people are going to reassess that.''

Most financial firms weighing whether to return are not concerned with future terrorist attacks as much as with damage from the recent one. Mermel said companies' main worries are possible environmental hazards and the problems of bringing employees into an area ringed with crushed subway tunnels.

A total of 13.4 million square feet of office space was destroyed in the Trade Center attack, and 18.5 million square feet was damaged, according to Tenantwise. TenantWise estimated that financial services firms have taken 4.4 million square feet of office space outside the city since Sept. 11.

American Express has taken out short- and medium-term leases on new offices in Parsippany and Short Hills, N.J., and in Stamford, Conn. Spokeswoman Molly Faust said that the company is ``committed to having our headquarters in New York City,'' but that it is too soon to say whether it will return to all of its downtown office space.

Lehman Brothers is buying a 1-million-square-foot office building near Times Square after much of its work force was displaced from the company's headquarters in the World Financial Center.

Lehman spokesman William J. Ahearn said that the company retains ``a commitment to downtown,'' but that it is too early to say whether it will return to the World Financial Center, which is not expected to reopen for several months.

``It's got nothing to do with uptown, downtown, East Side, West Side,'' Ahearn said. ``What we were looking for was something with enough space that could accommodate our trading activities.''

Even the Nasdaq Stock Market is considering moving its headquarters to midtown from One Liberty Plaza, a 53-story building next to the fallen towers.

Cushman & Wakefield, which manages or leases 22 percent of the area's premium office space, reported that 46 displaced companies have struck new deals for midtown space, while only seven have committed themselves to new downtown space. Several others have moved to New Jersey and Connecticut.

``There's certainly people who have reservations about downtown and being downtown,'' Cefaly said. ``And people who leave temporarily - it's difficult to get them to come back.''

Employees who work downtown say it is hard to ignore what happened blocks away.

The financial district's crown jewel is now a smoking pile of rubble and human remains. National Guardsmen in camouflage have joined the dark suits and pinstripes that flow along Wall Street's sidewalks. The wind carries the acrid smell of burning debris.

``There's a real nervous feeling in the air. It interferes with work,'' said Jack Vilacius, 27, a Wall Street broker. ``You can't concentrate, you're constantly looking out the window.''

Vilacius said he worries about another terrorist attack in lower Manhattan - a sentiment echoed by others.

``Prior to Sept. 11, I loved working downtown. Since then, the anxiety level's certainly higher,'' said David Basoco, 36, who works at a financial services firm. ``During the day, everyone's busy, but I don't think there's anybody that, somewhere in the back of their mind, doesn't worry."