A crane collapse at a South Korean shipyard run by Samsung has killed six people and injured more than 20 others, says the Yonhap news agency.
Rescuers have been searching for people trapped after Monday's incident at Geoje near Busan.
The victims are understood to be subcontractors working for shipbuilder Samsung Heavy Industries.
The incident has shocked South Korea which has a relatively low rate of industrial accidents.
The oil platform was being built for French firm Total, for use in its Martin Linge oil field in the North Sea off Norway.
"The crane fell onto the platform's well bay module, where the people were working," Total spokesman Leif Harald Halvorsen told Yonhap.
"For the time being, all work at the yard has been stopped and the investigation is ongoing."
He added no Total employees were among those killed or hurt.
Samsung Heavy Industries is the world's third biggest shipbuilder, and is also involved in other engineering work.