A nighttime fire ripped through a rundown five-story building in Johannesburg that was occupied by squatters and homeless people, killing at least 73 people, emergency services in South Africa’s biggest city said.

Some of the people living in a maze of shacks and other makeshift structures inside the building threw themselves out of windows on Thursday to escape the fire and might have died then, a local government official said. Seven of the victims were children, the youngest a one-year-old, according to an emergency services spokesperson.

As many as 200 people may have been living in the building, witnesses said.

Emergency crews expected to find more victims as they worked their way through the building, a process slowed by the conditions inside. Dozens of bodies were lined up on a nearby side road, some in body bags, and others covered with silver sheets and blankets.