At least six workers died and 20 others were injured after a crane overturned at a shipyard run by Samsung in South Korea on Monday (1 May).

The incident took place at the Samsung Heavy Industries' shipyard in the southeastern port city of Geoje around 2.50pm local time (5.50am GMT). Two cranes collided causing a structure to fall from one of the cranes, according to Seoul-based Yonhap news agency.

The victims were thought to have been subcontractors working for Samsung Heavy Industries.

The South Korean shipbuilder said rescuers were searching for workers who might have been trapped under the debris after the 32-tonne crane fell on a ship.

The cranes were involved in the construction of an oil platform for French energy company Total's Martin Linge 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."

No Total employees were killed or injured in the incident, he added.

Total is unsure about the extent of the possible damage to the platform, Reuters reported the company's spokesman in Norway as saying. Samsung Heavy also said it was not clear how the crane collapse might affect the completion and delivery of the oil platform. It is believed that Total was expecting to start producing oil and gas in the North Sea in 2018.

Authorities in South Korea said they will launch an investigation to find out if there was any breach of security regulations at the construction site and if there were any operational mistakes committed by the crane drivers or security supervisors.

The crash is reported to have come as a shock as South Korea is known to have a relatively low rate of industrial accidents, the BBC noted.

Samsung Heavy Industries, the world's third largest shipbuilder, is also involved in other engineering work.

Samsung crane collapse
A view of the accident site after a crane collapsed at a Samsung Heavy Industries shipyard in Geoje, South Korea, 1 May 2017 in this still image taken from video Geoje Fire Station/Handout via Reuters TV