After a night of frantic searches through the rubble of a Brooklyn building collapse that killed eight people, New York City officials announced on Thursday that they were ending their rescue efforts, concluding there were no more victims.

Eighteen other people, including four firefighters, were injured in the collapse and its aftermath at 1321 Flatbush Avenue. Two children who were cousins were among the eight killed, according to an internal police report. Three were construction workers.

The tragedy shattered the heavily immigrant neighborhood and set off a city investigation into excavation at the construction site next door at 2625 Bedford Avenue.

The collapse occurred around 4 p.m. on Wednesday. James Williams, who works at a deli across the street, said he had been hearing an incessant loud hammering noise every few minutes from the construction site on Wednesday afternoon. He went outside and saw bricks falling from 1321 Flatbush, a three-story apartment building. “I’m like, Oh hell, what is going on?” he said.

He watched as the building started to crumble, its front and side sliding away, and a check-cashing shop that he frequented underneath all collapsing into the open construction site next door. He saw clothes and a microwave oven thrown into the dust-filled air. He heard people scream.

The first firefighters arrived within a minute, followed by more from around New York City and from New Rochelle, N.Y., in Westchester County. The search and rescue efforts involved about 250 personnel in all.