(AP) - Rescuers dug through debris Sunday for threepeople still missing in the rubble and wreckage left when aconstruction crane toppled like a tree across a city block andkilled at least four construction workers.

Among the missing were two workers and a woman who was stayingin an apartment at a town house flattened by the crane.

"Each passing hour, things get a little more grim," FireCommissioner Nicholas Scoppetta said. Twenty-four others wereinjured, including 11 first responders, said Mayor MichaelBloomberg. Eight remained hospitalized Sunday, officials said.

The crane rose 19 stories and was attached to an apartment towerunder construction when it broke away Saturday and toppled like atree onto buildings as far as a block away.

On Sunday, crews continued to remove pieces of the crane andpiles of debris from the damaged buildings as neighborhoodresidents and a Manhattan borough official raised concerns aboutcity inspections at the apartment tower.

"I warned the Buildings Department on March 4 that it was notsufficiently braced against the building," said Bruce Silberblatt,a retired contractor and vice president of the Turtle BayNeighborhood Association.

Retired ironworker Kerry Walker, who with his wife lived in thetop-floor apartment of the four-story town house and left minutesbefore the collapse, had complained that the crane appeareddangerously unstable, his stepson said.

"He knows all about cranes and said this one had no braces,everything was too minimal," John Viscardi said. "He told onefriend on the phone that 'if you don't hear from me, it's becausethe crane fell on my house."'

The crane was attached to an apartment tower under constructionon East 51st Street east of Second Avenue when it broke away fromits anchors Saturday and toppled south, crashing into buildings on51st and 50th streets.

Next to the destroyed brownstone, a six-story gray apartmentbuilding on 50th Street and Second Avenue was missing an uppercorner, as if a giant had clawed it. Dusty furniture and paintingswere visible from the street.

City officials said the crane was inspected Friday. At daylater, it was being lengthened with a new section, a process knownas "jumping," when it fell.

Bloomberg said mechanical failure or human error may have causedthe accident. "As far as we can tell, all procedures that werecalled for were being followed," he said.

Bloomberg said that about 250 cranes are operating in the cityon any given day, and the accident should not alarm New Yorkersliving near high-rise construction sites.

"Do I think that you should worry if there's a crane across thestreet? No," Bloomberg said. "This is such a rare thing that Idon't think we should worry about it."

The city had issued 13 violations in the past 27 months to theconstruction site where a 43-story high-rise condominium was goingup. "Every large construction site has violations," Bloombergsaid.

Manhattan Borough President Scott Stringer said Bloomberg shouldform a multi-agency task force to inspect major constructionprojects.

"It is unacceptable for the Department of Buildings to sayyesterday that the 13 open violations on this construction sitewere ... business as usual," Stringer said. "We can't keep goingon like this."

Killed were construction workers Wayne Bleidner, 51, of Pelham;Brad Cohen, 54, of Long Island; Anthony Mazza, 39; and AaronStephens, 45, of New York City, police said. Family who answered atthe homes of Bleidner and Mazza had no comment Sunday.

The missing woman had come from Miami to celebrate St. Patrick'sDay and visit a friend who lived in the brownstone, said JohnLaGreco, owner of Fubar, a saloon on the ground floor.

She was in her friend's second-floor apartment at the time ofthe collapse, he said. Her friend was rescued, he said.

On Sunday, the Reliance Construction Group, the project'scontractor released a statement expressing sympathy to the familiesof the dead and the injured and said it was cooperating withgovernment investigators.

Reliance said it had subcontracted different parts of the joband that New York Crane owned the crane. A telephone message leftwith New York Crane Sunday wasn't returned.

The collapse comes amid a building boom in New York City andfollows 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 beingdismantled fell and crushed a taxi cab.