A crane undergoing deconstruction collapsed at a shipyard in Busan on Wednesday killing four workers.

At about 9:46 a.m., the crane’s machine room fell about 20 meters to the ground immediately killing four workers, including one who was crushed by the debris.

The authorities believe that the workers, employees of a demolition contractor, were in the process of detaching the machine room from the 40-ton crane.

According to reports, three of the workers were cutting through structures holding the machine room in place, while another was working inside the machine room.

A fifth worker assigned to the project escaped unhurt as he was overseeing the operations from the ground.

The shipyard was initially believed to belong to Daesun Shipbuilding and Engineering Co., but it was later revealed that the company had sold the facility to Geocheong Shipbuilding Co. in December.

Geochung is a supplier of ship parts, and the crane was being dismantled as part of the company’s plans to convert the plot occupied by the structure for a different use.

The police plans to question witnesses and officials of the contractor to determine whether safety protocols were followed.

By Choi He-suk (cheesuk@heraldcorp.com)