"I felt the first building collapse. I saw the second tower collapse," Soriano said. "It collapsed from the outside in."

"Those terrorists are real cowards," he said.

Tyler Catalana, 23, a resident of Mill Valley, Calif., who is studying architecture in New York, said he saw the north tower collapse into itself.

"It looked like a nuclear war," he said.

Catalana said that when the dust began to settle, "it looked like the surface of the moon."

Much of lower Manhattan was evacuated as officials feared potential gas leaks and falling debris could cause further casualties.

Like refugees fleeing a war-town nation, tens of thousands walked across the Brooklyn Bridge and along a nearby highway as they sought safety.

Some people wore paper masks to block out the dust. People gathered around cars listening to news over their radios. Others washed off the dust with the water from open fire hydrants.

Giuliani said the New York Stock Exchange was intact, but he doubted it would reopen today, because it was necessary to keep lower Manhattan clear for emergency vehicles. Public and parochial schools in the city were scheduled to be closed.

"New York is still here. The World Financial Center is still here," the mayor said. "We have undergone tremendous losses and we will grieve for them horribly. We are going to prevail."

Three large trucks arrived at the city morgue in the afternoon with extra supplies. A spokesman said that bodies were expected later.

Families searching for missing relatives were directed to an office where city employees took information. Extra medical examiners were summoned to the morgue.

The most severely burned were taken to a center at New York Presbyterian Hospital on Manhattan's upper East Side. Elective surgery at the hospital was canceled. Patients in the emergency room watched the disaster on television.

Tiffany Keeling, 32, of New Mexico was treated at Bellevue Hospital for smoke inhalation and head injuries. She said she was attending a training seminar for financial consultants on the 61st floor of the south tower of the trade center.

"We were looking out the window and the entire sky was filled with paper," she said. "We thought it was a ticker tape parade."

Then, Keeling said, she noticed a huge cloud of smoke billowing from the north tower. "Fireballs were falling to the ground, which I now know were people."

Keeling and the other trainees headed for the stairs. When they were between the 59th and 58th floors, a voice on the building's public address system said the north tower was the only structure in danger and that everyone could return upstairs. Half of her group went back up. She and others continued to the street.

"People were coming down from the top floors in every condition you could imagine," Keeling said, through tears.

"I heard a woosh like air getting sucked in a vacuum. I grabbed my jacket and got as close to a planter as possible and started feeling little things on my back like hail, and they got bigger and bigger until the air was solid debris."

Keeling said she turned to a man who walked down the stairs with her and asked: "Are we dead?"