Police and labor authorities raided the headquarters of HJ Shipbuilding and Construction as part of an investigation into a boiler tower collapse that killed seven workers. 

About 50 investigators from the Ulsan Police Agency and the labor ministry's Busan regional office seized documents related to the collapse and accident records from a contractor that performed demolition work.

Authorities also plan to examine whether the necessary safety measures were implemented to prevent collapse during the dismantling process.

The labor ministry’s regional office said that it will review the work instructions exchanged between the contractor and subcontractor, work methods and safety management systems to determine the structural causes of the accident.

The office warned that any violations of the Occupational Safety and Health Act or the Serious Accidents Punishment Act will result in strict accountability.