Four workers were killed, and six others were injured when part of a highway bridge under construction collapsed in South Korea on Tuesday morning, officials said.

By the afternoon, all 10 workers who were at the site were accounted for, South Korea’s National Fire Agency said, after emergency crews had searched through the rubble for victims.

The collapse happened about 9:50 a.m. local time near the city of Cheonan, which is about 50 miles south of Seoul, the capital.

It occurred 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.

The workers were operating a crane while doing work involving a support column, Koh Kyung-man, a representative of Anseong Fire Station, said at a news conference.

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