At least one worker is dead after a bridge collapsed at a highway construction site in the central city of Cheonan.

Authorities said that as of around 11 a.m. Tuesday, one worker is dead and another has been found without vital signs at the site in Cheonan, South Chungcheong Province, while three others are critically injured and one has a minor injury. 

The fire agency said eight workers are believed to be trapped in rubble and rescue efforts are underway.

The authorities have mobilized 18 pieces of firefighting equipment and 53 officials for the rescue. 

The fire agency said earlier that it received a report around 9:50 a.m. that the collapse occurred at the construction site and put a Level Two response posture in place.

Fire authorities suspect that a structure on the bridge pier collapsed during construction. 

About ten minutes after activating the Level Two response posture, they issued an order mobilizing firefighters and national firefighting resources to ensure a comprehensive national response.