CNN  — 

At least eight people were injured when a building they were working on partially collapsed in New Haven, Connecticut, on Friday, according to officials.

The building was under construction when a portion of the second floor collapsed onto the first floor and into the basement, Mayor Justin Elicker said in a news conference. A total of 36 people were working at the site.

The partial collapse occurred as workers were pouring concrete, Elicker said. Part of the second floor collapsed onto the first floor and into the basement.

Firefighters rescue a worker after the partial collapse of a building under construction on  Friday in New Haven, Connecticut.

Three victims were trapped and needed to be rescued from the concrete before the drying process started, Alston said.

New Haven Fire Chief John Alston Jr. said in a news conference that it appears that the collapse occurred while workers were pouring concrete that pooled faster than they could spread evenly. Alston added that three victims were trapped and needed to be rescued from the concrete before the drying process started.

All of the victims are construction workers, Lenny Speiller, the director of communications at Elicker’s office, told CNN.

The collapse happened on Lafayette Street. Photos of the scene show people being rescued via high-angle rescue operations. At around 2 p.m., the Connecticut Fire Photographers Association tweeted that the fire department had “successfully removed all victims trapped in the debris.”

The federal Occupational Health and Safety Administration is on site, and an immediate stop work order was being issued, according to the fire chief.

New Haven is located in central Connecticut.