CAPE TOWN, South Africa – A multi-story apartment building under construction collapsed Monday in a coastal city in South Africa, killing two construction workers and leaving 53 trapped under the rubble, authorities said.

An additional 20 workers were pulled from the mangled wreckage of the building and were being treated for injuries at various hospitals, city authorities said.

The building collapse happened just after 2 p.m. in the city of George, about 400 kilometers (250 miles) east of Cape Town on South Africa’s south coast.

Hours later, more than 100 emergency personnel were at the site and were likely to work through the night, using sniffer dogs to try and locate survivors, some of whom were feared buried under huge slabs of concrete.

Cranes and other heavy lifting equipment were being sent to help with the rescue effort, the George municipality said, while more emergency responders were being brought in from nearby towns and cities. They were expected to reach the site at about midnight.

There were 75 workers at the building site when it collapsed, and family and friends were gathered at the nearby municipal offices waiting for news, the municipality said.