At least three workers were killed and five others were injured when part of a highway construction site collapsed in South Korea on Tuesday morning, officials said.

Emergency crews were searching through the rubble for victims, South Korea’s National Fire Agency said. The collapse happened about 9:50 a.m. near the city of Cheonan, which is about 50 miles south of Seoul, the capital.

The collapse happened during the construction of a bridge connecting sections of the highway, Yonhap, a South Korean news agency, reported. Five steel beams supporting the bridge, each about 164 feet long, collapsed one after another, the news agency said.

A video published by Yonhap shows part of a structure supported by columns breaking into pieces and plunging to the ground.

This is a developing story.