An iron concrete mould collapsed Wednesday at a construction site in South Korea, leaving eight people injured and one missing, police said.

The accident happened at around 3.25 p.m. in Gwangju, south of Seoul, when the mould fell on the fourth floor of a building under construction. Nine people working on the rooftop also fell down during the collapse.

   Eight of them were rescued and transported to nearby hospitals for treatment, but one remains missing, according to police.

   The exact cause of the accident is under investigation. Police suspect that the mould collapsed as it could not sustain the heavy weight of concrete being poured onto the building's rooftop.