Rescue crews have continued to search for survivors in the rubble of a collapsed building in Brooklyn, New York, as the death toll rose to eight.

Authorities in New York City said at least 17 people were hurt when the three-storey residential building on the edge of a construction site in the borough’s Flatbush neighbourhood collapsed at about 4pm on Wednesday.

Four people were critically injured, officials said, and at least seven children were among the casualties. It is not clear if any of the fatalities are minors.

Zohran Mamdani, the mayor of New York City, said in a post on X on Thursday morning that he was “heartbroken” by the tragedy. “Eight New Yorkers have now lost their lives and at least 17 have been injured, including three firefighters,” he wrote.

Zohran Mamdani said the conditions around the building were ‘extremely dangerous’ and urged people to stay away from the area. Photograph: Charly Triballeau/AFP/Getty

“There are no words for a loss of this magnitude. My heart is with the families and loved ones of those we have lost, those who are injured and everyone grieving today.”

He urged the public to stay away from the site on Flatbush Avenue, where about 250 first responders from the New York City fire department (FDNY) worked through what Mamdani said were “extremely dangerous conditions” to find anybody still trapped.

The department, in an emailed statement to the New York Times on Thursday morning, said it was still hopeful of locating survivors.

Workers brought in an excavator in the early hours of Thursday to help move larger pieces of wreckage from the building, which had housed a number of apartments. Drones and canine units were being used to assist the rescue effort.

Video taken at the scene on Wednesday night showed crews removing several people on stretchers. One person, seen covered in dust, was extricated at about 6.30pm after a crew dug a hole through some of the debris.

The building had housed a number of apartments. Photograph: Charly Triballeau/AFP/Getty

Another person rescued was a woman who was six months pregnant, whose husband had been searching for her through the late afternoon, New York ABC News affiliate WABC reported.

“I have an update. She is alive, she is still alive. I am very happy,” the man told the outlet.

Dozens of onlookers, some in tears, gathered to watch the rescue operation. Lillian Bonsignore, the FDNY commissioner, told a crowd at an evening press conference: “We know that we are not finished here, and we will likely not be finished for quite some time.”

Adding to the urgency of the situation was a weather forecast that predicted heavy rain with a chance of thunderstorms and gusty winds moving through the borough from lunchtime and through Thursday afternoon.

Rescuers searching for people in the rubble a day after the Brooklyn building collapsed. Photograph: Charly Triballeau/AFP/Getty

Several people who were made homeless by the collapse took shelter in the Bethesda church of God in Christ opposite the site.

The building that collapsed was perched at the edge of a lot where another one-storey building had been torn down for a construction project. The site was being excavated and the building that fell down filled the construction pit with bricks and wood.

Another building that shared a wall with the collapsed structure remained standing, but its wall was shorn off, exposing the rooms inside, including a bedroom and closets filled with clothing.

Investigators from New York City’s department of buildings were at the scene beginning an investigation into the cause of the collapse.

A first responder on a crane illuminates the scene with a flashlight. Photograph: Ryan Murphy/AP

News channel NY1 reported that the department had recorded several issues with a project next door to the collapsed building in May, including working while there was a stop work order, not having proper overhead protection for the neighbouring properties, and failing to conform to approved construction drawings.

The city’s department of housing, preservation and development has recorded almost 100 violations at the collapsed building dating to 1972, NY1 said.

Property records show the building as a three-story construction containing four residential units and one commercial unit.

The Associated Press contributed reporting