The collapse occurred at 1 Congress St. around 5:40 p.m., officials said. Police said a man operating a crane was killed when his crane went down to about nine floors with a large amount of debris. The employee’s name is not known. A passerby was also taken by the Boston EMS to a local hospital but was not physically injured. “This is a horrific tragedy and my heart goes out to the family and loved ones of the worker here tonight,” said Boston Mayor Michelle Wu. “Our thoughts and prayers are with the worker during this terrible time,” added City Councilman Ed Flynn, who represents the neighborhood. “Our prayers are with him, his family, and I know the city will support this worker and his family. It is a difficult time, but this city remains united – especially in difficult times.” One person was killed as a result of a partial collapse of a building in the garage of the Government Center. The demolition is part of Bullfinch’s $ 1.5 billion reconstruction project. The completed project is expected to include a parking garage surrounded by office buildings and apartment buildings. The site has been under demolition for quite some time. “This is a very complex site and we know that risk workers should never worry, their family should never worry about going home at night,” Wu said. He said the city would do “whatever it takes to find out what happened here”. The Occupational Safety and Health Administration is on the scene investigating the collapse. The project is located just above a row of Massachusetts Bay Authority Orange Line tunnels, and public safety officials are currently working to ensure the stability of the parking garage and the tunnels below. As a result, heavy traffic impacts on the roads and in the MBTA are expected in the coming hours. “Right now a large part of this part of the city is being quarantined until we can determine if it is safe and the tunnel rails below are safe,” said Boston Police Capt. Kelley McCormick. Boston Police issued a traffic alert along Massachusetts Avenue between Commonwealth Avenue and Boylston Street, which will be closed until Monday morning due to construction. Travelers are advised to look for an alternative route. “We will work very quickly to make sure that as soon as possible, transport, traffic and everything can start again,” the mayor said on Saturday night. “We ask people to be patient.” John Moriarty & Associates, the company that oversees the construction, confirmed that one of its workers died at the construction site after a concrete slab fell from the ninth floor on the east side of the Haymarket garage and collapsed on the eighth floor. “Our heartfelt thoughts and condolences are with the family of the worker who lost his life,” the company said in a statement. “JMA remains committed to providing a safe and healthy workplace for all our employees and business partners.” Suffolk County Attorney’s Office Kevin Hayden also issued a statement saying he would be involved in the investigation into the tragedy. “Our office is a stone’s throw from the garage and our staff is watching from the windows of his office all the work that has been done over these many months,” Hayden said in a statement. “Knowing that one of the workers in this project died tragically weighs on our hearts. Our deepest condolences are expressed to his family and friends.”