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Carelessness, poor procedures may have caused deadly Seoul overpass collapse, say experts and witnesses

Published: 27 May. 2026, 19:06 Updated: 27 May. 2026, 19:33

Debris is seen at the scene one day after part of the deck collapsed at the Seosomun Overpass demolition site in Seodaemun District, western Seoul, on May 27. [NEWS1]

A lack of safety measures and the simultaneous entry of multiple inspectors onto a weakened structure may have been key factors in the partial collapse of the Seosomun Overpass on Tuesday, according to witness accounts and experts. Three people were killed in the accident in Saedaemun District, western Seoul.

“The team leader climbed between the girders to inspect whether work could resume, and the structure immediately began collapsing once [the additional] weight was applied,” a Seoul Metropolitan Government official who witnessed the accident said. “The structure appears to have been weakened during the demolition process.”

On Tuesday afternoon, a section of Seosomun Overpass collapsed during demolition work. The overpass, which was built in 1966, was being dismantled due to aging and safety concerns. Demolition began on Aug. 17 last year and was scheduled for completion in early June.

Demolition work had been suspended at around 2:30 a.m. on Tuesday after a 2.9-centimeter (1.1-inch) depression formed during work to dismantle the overpass's upper deck. Thirteen experts had entered the structure simultaneously to inspect the issue, and the collapse reportedly began shortly afterward.

A full-scale safety inspection involving outside experts did not begin until around 2 p.m., roughly 12 hours after the depression formed in the deck at 2:30 a.m. Construction firms and related parties had conducted internal inspections during the morning.

“It is standard procedure to put sufficient safety measures in place before conducting a full safety inspection,” Ahn Hyeong-jun, an architecture professor at Konkuk University, said. “Allowing multiple inspectors onto an already weakened structure without any safety reinforcements increased the risk of collapse.”

Firefighters work at the scene of the Seosomun Overpass collapse accident in Seodaemun District, western Seoul, on May 26. [JANG JIN-YOUNG]

Some pointed out that detailed construction guidelines issued by the Seoul Metropolitan Government were not properly followed on-site.

The construction specifications for the overpass demolition project state that “safety facilities such as braces or support columns must be installed when necessary to prevent deformation, subsidence, or collapse of demolition structures and damage to adjacent facilities.”

“Work was carried out according to the demolition plan,” a Seoul Metropolitan Government official said. “There were no cases in which required measures were omitted or procedures violated.”

Experts argue that the failure to detect problems throughout the entire process — from planning to construction and supervision — was the core issue behind the collapse.

Part of the Seosomun Overpass lies on the ground after a partial collapse in Seodaemun District, western Seoul, on May 26. [YONHAP]

“If even one party — whether the construction firm, the supervisory team, the engineering company that drafted the plans or the Seoul Metropolitan Government overseeing the project — had worked properly, the collapse would never have occurred,” said Song Chang-young, professor at the Department of Architectural Engineering at Gwangju University.

“The demolition work plan itself may have been flawed, or workers at the site may have failed to properly follow the procedures outlined in the plan,” said Jung Jin-woo, professor at the Department of Safety Engineering at Seoul National University of Science and Technology.

Residents near the site also criticized authorities for underestimating the dangers posed by the aging structure.

Prior to the collapse, the Seosomun Overpass had faced repeated safety concerns, including falling concrete debris in 2019.

The scene of the Seosomun Overpass collapse in Seodaemun District, western Seoul, on May 26. [YONHAP]

The bridge received a D-grade rating — classified as poor structural condition and just one level above E, the lowest possible grade that requires immediate demolition — in a detailed safety inspection in 2019, before demolition work began last year.

“I previously filed complaints because pieces of concrete about the size of a finger would occasionally fall,” a resident surnamed Choi said. “I often thought it looked like it could collapse at any moment."

Police formed a dedicated investigation team led by the head of the Seoul Metropolitan Police Agency on the day of the collapse to determine its cause.

Investigators obtained related documents, including safety management plans, from the civil engineering department under the city government’s urban infrastructure headquarters. Police also conducted a joint forensic inspection at the site with the National Forensic Service and the Korea Occupational Safety and Health Agency through 4 a.m. on Wednesday.

Part of the Seosomun Overpass lies on the ground after a partial collapse in Seodaemun District, western Seoul, on May 26. [YONHAP]

Prosecutors separately launched a dedicated task force composed of four prosecutors and six investigators on Wednesday, led by Chief Prosecutor So Jae-hwan of the Seoul Western District Prosecutors’ Office.

“We will work closely with related agencies, including the police and labor authorities, to thoroughly determine the cause of the accident and where responsibility lies,” the Seoul Western District Prosecutors’ Office stated. “We will also do our utmost to ensure immediate support for the victims.”

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.
BY OH SAM-GWON, KIM YE-JUNG [[email protected]]