Five large underground hollows were discovered this week underneath one of Seoul’s road tunnels, city officials said Monday, adding to public concerns over safety sparked by similar discoveries in Seoul this month.

The newly found cavities are large enough to contain stacks of cars. They are located only a few meters away from two similar cavities discovered earlier this month below the Seokchon tunnel roadway in eastern Seoul.

Experts say the hollows under the road could cause it to abruptly collapse, creating a massive sinkhole that could kill hundreds. The previously discovered holes were up to 5 meters deep, while those found on Monday were up to 2.3 meters deep.

Seoul officials have filled parts of the hollows with cement as an emergency measure to prevent collapse, and are investigating nearby areas for additional holes. Parts of the Seokchon tunnel roadway have been fenced off with police tape.

The cause of the hollows is not yet known.

City officials suspect the ongoing construction of subway tunnels near the road created the hollows. Metro officials are constructing an extension to Seoul Subway Line No. 9 near the Seokchon tunnel.

But according to Ministry of Environment documents disclosed by Rep. Jasmine Lee of the Saenuri Party on Tuesday, underground hollows are often formed due to leaks in the sewers. Lee says 41 of the 53 sinkholes found throughout Korea since 2012 were caused by leaks in underground pipes.

Lee plans to question Environment Ministry officials during the annual parliamentary audits set to begin next Tuesday.

The lawmaker will also ask Finance Ministry officials to increase government funds for finding underground hollows and preventing sinkhole accidents.

“But I doubt the Finance Ministry will endorse such budget proposals,” Lee Seung-hun, an aide to Rep. Lee said. “Projects to fill up massive sinkholes in roads throughout the country will require billions of won.”

Monday’s discoveries follow the discovery of other hollows in eastern Seoul near a skyscraper that is still under construction. Since 2012, eight sinkholes have been found in Seoul. Although only three cars have been damaged by the sinkholes, who is responsible if hundreds are killed in a sinkhole disaster in one of Seoul’s bustling streets remains uncertain.

“It’s unclear which government bureau should take the lead,” a National Assembly official said.

The Seoul municipal government, the Ministry of Environment, and the Ministry of Land, Infrastructure, and Transport could all be responsible for damage caused by sinkholes in Seoul.

By Jeong Hunny (hj257@heraldcorp.com)