A kindergarten building in Seoul tilted Thursday night around 11:22 p.m. after the collapse of a retaining wall at a nearby construction site. The building was empty, and no one was injured.

According to local fire authorities and the Dongjak District Office, the accident at Sangdo Public Kindergarten occurred because construction of a nearby housing complex caused the ground to sink. 

The outer walls and pillars sustained damage, and experts warned that the kindergarten was at risk of collapsing. As of Friday at 1 p.m., the building leaned at an angle of about 20 degrees, according to the fire department.

The four-story building in southern Seoul opened its doors in April 2014 and had 122 students attending seven classes as of Thursday.

Seoul Mayor Park Won-soon visited the accident site in the morning and ordered a prompt, thorough inspection followed by the building’s demolition.

The Ministry of Land, Infrastructure and Transport conducted an overnight inspection and ordered a complete suspension of construction in the area. The 936.8 square meter construction site near the kindergarten was expected to accommodate 49 households upon the project’s completion. Construction had begun in May after some old row houses were torn down.

Authorities were already aware of the potential for an accident at the site, according to city education officials. The first sign of a problem became apparent in August, when a crack approximately 30 to 40 millimeters wide appeared in one of the floors of the kindergarten. 

“It was already discovered, during an inspection requested by the Sangdo Kindergarten in March, that the land in the area was weak due to the nearby construction. We delivered a report warning that it could collapse,” Lee Soo-kon, a professor of architectural engineering at the University of Seoul, told local media outlets.

“When an accident like this happens, someone will say it happened because of the rain. But construction work is not always done on sunny days. Rain is a factor that needs to be considered when you are planning a construction project,” Lee added.

A day before the collapse, the kindergarten’s principal had met with construction company representatives and officials from the district office. The builder promised to take measures to ensure safety.

After the accident, the kindergarten immediately closed its doors and notified parents of the emergency. The Seoul Metropolitan Education Office said Sangdo Elementary School will open up six classrooms for all of the 122 kindergarteners.

The accident has also alarmed parents with children at Sangdo Elementary School, which is only 2 kilometers away from the kindergarten. Police and education authorities have dispatched additional security forces to prevent students from going near the kindergarten.

By Jo He-rim (herim@heraldcorp.com)