NEW YORK - A crane rising 19 stories alongside a skyscraper under construction toppled like a tree across a city block Saturday, crashing into apartment buildings, killing four people and setting off a scramble for survivors.

The crane split into pieces as it fell, pulverizing a four-story townhouse and demolishing parts of three other buildings. One man was pulled from the townhouse 3 1/2 hours after the building was crushed.

Mayor Michael Bloomberg said at least four people, believed to be construction workers, have died and at least 10 people were injured in one of the city's worst construction accidents in recent memory.

The collapse devastated the affluent block on Manhattan's East Side: Cars were overturned and crushed. A huge dust cloud rose over the neighborhood. Rubble was piled several stories high.

"It's a horrible situation, very gory. There's blood in the street," said Lt. Gov. David Paterson, who takes over as governor for disgraced Eliot Spitzer on Monday.

An intensive rescue operation was under way to find anyone possibly trapped in the rubble on 51st Street near 2nd Avenue.

Fire Commissioner Nicholas Scoppetta said the rescue was "a painstaking hand operation, as we try to remove the rubble so we don't cause further collapse or injure anyone who may still be in that building." He said the operation would continue all night if necessary, including the use of search dogs and thermal-imaging and listening devices.