At least three construction workers died when scaffolding fell down a lift shaft at a building site in Hamburg, German authorities have said.

Several more people were believed to be missing under the wreckage.

People were evacuated from the site after Monday’s accident, the fire service in Germany’s second-biggest city said, per the country’s news agency dpa.

Between 1,300-1,500 workers were on site at the time.

The scaffolding appeared to have been eight floors above the ground before the collapse, with firefighters saying the rescue effort was difficult.

Officials initially said five people died. They later said they were sure of three deaths.

The accident happened in the Ueberseequartier, part of the port city’s HafenCity district.

HafenCity is a former port area on the Elbe river that is being redeveloped with office and residential buildings, hotels and shops.