Train operations on the Seoul-Busan line were normalized Thursday morning, a day after a KTX bullet train derailed in central South Korea and injured seven passengers, the operator said.

Korea Railroad Corp. (KORAIL) said trains bound for Seoul from the southeastern port city of Busan resumed normal operations from 5:47 a.m. and those heading to Busan from Seoul from 7:55 a.m.

The normalization came after more than 130 train operations were delayed or canceled Wednesday afternoon, as a KTX-Sancheon train derailed while passing a tunnel in Yeongdong of North Chungcheong Province, about 215 kilometers south of Seoul.

The derailment occurred at 12:58 p.m. Wednesday after the train was apparently hit by a steel structure that fell from the tunnel. Seven passengers suffered minor injuries in the accident, according to KORAIL.

Until 7:55 a.m., southbound KTX trains passing the section between the central city of Daejeon and the southeastern city of Daegu, connected by the Yeongdong tunnel, had to take a detour to slower lanes due to lengthy recovery work.

KORAIL said they completed safety inspections and a trial run before resuming services.

"We deeply apologize for causing inconvenience to train users," a KORAIL official said.

KORAIL will thoroughly investigate the exact cause of the accident in cooperation with related authorities and come up with measures to prevent such accidents from recurring, the official added. (Yonhap)