SEJONG -- A speeding van with 12 construction workers and others on board overturned on an expressway exit ramp in central South Korea on Monday, killing seven and injuring the five others, police and expressway officials said.

The fatal accident occurred on the Dangjin–Yeongdeok Expressway's Sejong section, about 120 kilometers south of Seoul, at 8:20 a.m., when the Starex van turned upside-down on a road leading to the South Sejong Toll Gate after colliding into a roadside signpost.

It was confirmed that the vehicle was speeding to overtake another car just prior to entering the curved exit ramp, where the speed limit is 40 kph, according to police and the Korea Expressway Corp.

The automobile was found to have lost its center of gravity and overturned after first impacting the signpost on the left side of the road while going around the ramp road that curves to the right, they explained.

The five injured people were transported to hospitals in Daejeon, they said, noting two of them were in serious condition.

It was also known that most of the passengers, except the driver, were not wearing seat belts, police said, adding an investigation is under way to determine the exact cause of the accident.

Most of the dead and injured passengers were reportedly day laborers, including Chinese nationals, who were returning to their accommodation in Sejong after failing to find work in Namwon in the southwestern province of North Jeolla due to inclement weather.

Six of the seven dead passengers and four of the injured are Chinese nationals, police said.

The Sejong City Police Agency said it has formed a special investigation team in charge of the van accident to thoroughly find out its cause.

The police agency also said it will consider various ways to support the injured passengers and the bereaved families in cooperation with Daejeon's police agency. (Yonhap)