A leaking gas line exploded during morning rush hour in the central city of Taegu on Friday, setting cars and buses on fire and killing at least 90 people.
The death toll, cited by Yonhap Television News, a division of the national news agency, was expected to rise as thousands of police and rescue workers searched the site.
The explosion in the provincial capital of 2.2 million people about 140 miles south of Seoul was caused when a spark from a subway construction site ignited gas escaping from a broken pipe, Yonhap TV said.
Hardest hit was an intersection crowded with morning commuters.
The explosion engulfed about 30 vehicles, including city buses, in flames. About 30 cars fell more than 30 feet into a construction site for a new subway line when the blast tore away metal sheets serving as a road over the excavation, Korea Broadcasting System said from the scene.
Ten buildings and houses near the intersection were destroyed, KBS said, adding that some 20 more cars were crushed and overturned.