Several more mysterious sinkholes have been discovered in Songpa district in southern Seoul, raising the total to seven and intensifying suspicions that subway excavation is to blame.
Seoul city officials discovered a 2.5 m deep sinkhole beneath an underpass in the district on Monday that stretches for 13 m. A couple of days earlier, four other sinkholes of similar sizes were discovered in the area.
The Seoul metropolitan government formed a taskforce of 11 experts earlier this month following the discovery of a series of sinkholes there.
City officials believe all the sinkholes opened due to subway excavation in the area. Construction workers are suspected of failing to fill in the gaps in the surrounding soil, which is mainly sand and gravel, making it highly susceptible to sinkholes if not plugged up properly.
The underpass has been off-limits for cars since Aug. 13, while city officials are monitoring the potential impact of the sinkholes on nearby buildings. A detailed survey is to follow.
A city official said, "No safety threats have been detected so far that could impact surrounding buildings."