South Korean Prime Minister Chung Hong-won on Friday visited the scene of an accident that killed at least 16 people at a pop concert in Seongnam.

The concert-goers were watching the pop group 4Minute earlier in the day when the ventilation grid they were standing on collapsed. Chung was taken around the scene of the accident by fire officials.

A fire official speaking at the scene said “because many people were on the ventilation grate” it collapsed, with many people falling to a basement.

He was seen looking into the ventilation hole that the victims fell into. Police later removed the ventilation lids from the scene of the accident. About 700 people had gathered to watch the concert, which was part of a local festival, the Yonhap news agency reported.

This report was compiled with inputs from The Associated Press.