Six people were found dead and about 20 others injured on Thursday in a fire that broke out in a tunnel along an expressway in Gwacheon, just south of Seoul, South Korean fire authorities said.
The blaze was reported to have occurred at 1.49 p.m. (local time) inside the tunnel along the Second Gyeongin Expressway that connects the western port city of Incheon to Seongnam City, Yonhap News Agency quoted the authorities as saying.
About 20 others were under treatment for smoke inhalation, they said, adding the death toll could rise further.
Initial findings showed the fire started after a bus and a truck collided.
It quickly spread to the tunnel, causing massive clouds of smoke.
About 50 fire trucks, 140 fire personnel and helicopters were sent to the scene to fight the fire
The exact cause of the fire is yet to be determined.