The site of a scaffolding collapse that killed 13 workers and injured 28 others in the central province of Ha Tinh on March 25. Photo: Nguyen Dung Police in Vietnam have banned 48 employees of a South Korean company from leaving the country, as they are investigating a catastrophic scaffolding collapse that left 13 people dead and 28 others injured in the central province of Ha Tinh last week.

The employees of Samsung C&T, a subsidiary of Samsung, are Korean nationals, according to local media.

Nguyen Duc Thuan, chief of Ha Tinh’s immigration division, said Monday that the temporary ban is in place because investigators need to question the staff about the accident that happened at the construction site of a steel mill-port complex on March 25.

Investigators, including those from the Ministry of Public Security’s forensic institute, have not reached any conclusion on the cause of the accident that is deemed as the worst in Vietnam’s construction sector since 2007, Phan Ke Hien, spokesman of Ha Tinh’s police department, was quoted as saying in news website VietNamNet.

Official reports by the province’s authorities showed that around 50 workers were working on the scaffolding, which was 25 meters high, 40 meters long and 35 meters wide, when it tumbled down on the night of March 25.

Some survivors told local media that about 30 minutes before the collapse, the scaffolding shook strongly. Many of them ran away, but a few minutes later their foreign supervisor ordered them to come back to continue working.

The structure was part of the construction of a breakwater to protect the port.

The whole complex in Vung Ang Economic Zone is invested by Taiwanese-owned Formosa Plastics Group with the initial investment of nearly $10 billion. Construction work started in July 2008.

The most recent catastrophe at this scale took place on September 26, 2007, when two spans of a bridge which was being built in the Mekong Delta collapsed, killing 55 workers and injured 80 others.

Work on Can Tho Bridge, which connects Can Tho City and Vinh Long Province, was completed in 2010.