A vacant building recently cited for loose bricks and other violations collapsed in New York City Thursday morning, leaving a mound of rubble and injuring three people.

A portion of the five-story building at 71 Reade Street in lower Manhattan came crashing down at about 6:15 a.m. Thursday.

New York City Buildings Department officials say it was under construction and unoccupied at the time of the collapse.

Emergency crews with a dog searched the site and a neighboring building as a precaution, and three people — two firefighters and one civilian — were treated at a hospital for minor injuries, fire officials said. Their conditions weren't available.

Lewis Largent, who lives directly across the street, was looking out the window at 6:15 a.m. when "the bricks started trickling off the top corner. I was thinking was it raining or something. Then within 10 seconds it just all came down like a wave or an avalanche."

The building was cited Wednesday for several violations, including wobbly bricks and cracks throughout its north and west sides, according to city records.

On Tuesday, the city cited it for being vacant, open and unguarded after a caller complained the building was abandoned. And on April 10, the property was cited for having unrepaired cracks on its parapet and window sills.

Buildings Department inspectors combed the scene, about seven blocks north of the World Trade Center site, and worked to ensure that the rest of the structure didn't fall.

The cause was not immediately determined.

Gas was shut off in the area, and Reade Street was closed.

The front half of the building appeared to have been sheared off in the collapse, and interior floors were visible from the street. Piles of bricks were on the ground, and pieces of wood were hanging from what remained of the structure. A car on the street was covered in rubble.

Some work was being done to shore up the building, which is next to a construction site, according to Buildings Commissioner Robert LiMandri. Inspectors had been there this week.

The collapse occurred before the normally busy flow of pedestrians and traffic.

The neighborhood is part of an officially designated historic district in the Tribeca section of Manhattan, but the crumbling building was constructed in the late 1980s. Demolition was underway Thursday afternoon, said buildings spokesman Tony Sclafani.

A neighborhood businessman said he was worried about a homeless man who often slept outside the structure. Kody Tokar, who owns an elevator company across the street, arrived about 45 minutes after the collapse.

He said the homeless man was "always sleeping there," under scaffolding in front of the building.

Tokar said he saw bricks dropping off the building on Wednesday, and also noticed some cracks. He and others who work in the neighborhood had joked in the past that they didn't want to park there.

"The building looked like it was going to fall for a while," Tokar said.

He said 71 Reade Street had been empty for several years. There was excavation in the lot next door, where there was construction under way, he added.

Lisa Schiller, a 20-year resident of the neighborhood, was shaken by the collapse.

"We're a little freaked out about it," Schiller said when she came out for her morning walk and saw the commotion.

Additional coverage from MyFOXNY.com.

The Associated Press contributed to this report.