Crews with search dogs and heat-sensing cameras sought survivors — or more victims — today in the rubble of an apartment building crushed in a giant crane collapse that killed four people and injured at least 17.

Mayor Bloomberg called the collapse, at a new high-rise condo building, one of the city’s worst construction accidents.

“I heard a big crash, and I saw dust immediately,” a 66-year-old retired banker who was lying in bed talking on the phone when she glanced out her window and saw bricks raining from the sky, Maureen Shea, said. “I thought the crane was coming in my window.”

The crane broke into pieces as it fell yesterday afternoon, pulverizing a four-story townhouse and demolishing parts of five other buildings. Cars were overturned and crushed. A dust cloud mushroomed over the neighborhood. Rubble piled several stories high.

“It’s a horrible situation, very gory. There’s blood in the street,” said Lieutenant Governorr David Paterson, who is to be sworn in as governor tomorrow.

Several blocks were closed and some residents spent the night at a nearby high school serving as a Red Cross shelter.

Today, construction crews positioned a second crane to help remove pieces of the white crane that crushed the townhouse, and started removing piles of bricks and other debris from the street.

The Fire Commissioner, Nicholas Scoppetta, said rubble was being painstakingly removed, sometimes by hand, to prevent further collapse.

The crane that fell had stood at least 19 stories high and had been attached at various points to the side of a half-built apartment tower. The crane was to have been extended yesterday so workers could start work on a new level of the planned 43-story building, said an owner of the company that manages the construction site.

A piece of steel fell and sheared off one of the ties holding it to the building, causing the structure to detach and topple, an owner of the Reliance Construction Group, Stephen Kaplan, said.

“It was an absolute freak accident,” he said yesterday. “All the piece of steel had to do was fall slightly left or right, and nothing would have happened.”

Killed were workers Wayne Bleidner, 51; Brad Cohen, no age available; Anthony Mazza, 39; and Aaron Stephens, 45, police said today.

Reliance issued a statement today expressing sympathy to the families of the dead and injured and said it was cooperating with investigators.

“We have already launched out own internal investigation to understand exactly what caused this tragedy,” the company said.

Mr. Kaplan said the company had subcontracted the work to different companies and was not in charge of the crane. Phone messages and an e-mail seeking comment from the crane’s owner, New York Crane & Equipment Corp., were not returned.

“There are no words to describe the level of devastation we feel today as a result of this tragic event,” the lead partner at East 51st Development Company, which owns the property, James Kennelly, said in a news release.

The owner of the Fubar tavern on the townhouse’s ground floor, John LaGreco, returned today to the devastated scene where an employee and a second person in the bar, which was closed, had been rescued, he said.

“It’s unbelievable that this happened,” Mr. LaGreco said. “We’re going to sue the hell out of them, of course.”

At least 17 people were hurt. Eight remained hospitalized today, including three in critical condition, fire department officials said. Nine others were treated at the scene, including five firefighters, officials said.

No one else had been found in the demolished brownstone today, authorities said.

Residents of the affluent block on Manhattan’s East Side said they were grateful the accident occurred on a weekend when fewer people are in the area.

“We would be dead if it wasn’t on a Saturday,” an assistant for an artist who had office space in the crushed townhouse, Bryan Beus, said.

Some residents said they had complained to the city several times about the construction site. Crews worked illegal hours and the building was going up too fast, they said.

City officials said they had issued 13 violations to the site in the past 27 months, a normal amount for a project of that size. Inspectors had examined the crane Friday and found nothing wrong with it.

City Building Department records show a caller told officials March 4 that the upper portions of the crane appeared to lack the proper number of safety ties attaching it to the building. A city inspector visited the site and determined March 6 that no violation was warranted.

The collapse comes amid a building boom in New York City and follows a spate of construction accidents in recent months, including a few involving cranes. In 2006, a 13-foot piece of a crane mast that was being dismantled fell and crushed a taxi cab.

Last month at a Donald Trump hotel-condo tower, a worker plummeted 40 stories to his death when a concrete form gave way. A month before that, a crane’s nylon sling broke away and dropped seven tons of steel onto a construction trailer across from ground zero, injuring an architect.