South Korean police said Sunday no safety personnel were deployed at an outdoor pop concert where a ventilation grate collapsed, killing 16 people and injuring nine others.

"From the beginning, there were no safety personnel for the concert," a police spokesman told reporters, according to Yonhap news agency, after about 20 people were questioned over the incident Friday in the city of Seongnam south of Seoul.

Those questioned included officials of Edaily, a domestic Internet news provider which financed and organised the concert attended by more than 700 people, Yonhap said.

A local government official in charge of safety committed suicide Saturday by jumping off a building near the site after he was questioned by police.

The victims were standing on a ventilation grating to get a better view when the structure collapsed under their weight, sending them plunging 18.7 metres (62 feet) into an underground parking area.

Amateur video footage obtained by television stations showed shocked spectators surrounding the collapsed grate as the popular all-girl K-pop band 4Minute, apparently oblivious to the accident, continued performing on stage.

Witnesses have told media there were no security guards or safety fences to prevent spectators overflowing, with dozens of people chanting and dancing on the grating despite warnings by show organisers.

Edaily chairman Kwak Jea-Sun apologised to the victims' families and said he would take responsibility for the tragedy, including compensation.

"An unexpected incident happened due to structural problems and negligence," he said.

Experts described the incident as another "man-made" disaster.

"Over the past decades, economic expansion always took precedence over safety concerns, resulting in a lack of safety consciousness among Koreans," said Seoul National University professor Chung Jae-Hee.

The country is still grappling with the aftermath of the Sewol ferry disaster in April that left more than 300 dead, most of them high school students.

That tragedy prompted government promises of a national review of safety standards, as it became clear that poor regulatory oversight was a major contributor to the scale of the tragedy.

In February the roof caved in at a student-packed auditorium near the southern city of Gyeongju, killing 10 people and injuring more than 100. An investigation found structural flaws and lax management controls.

In 2005 11 people were crushed to death and nearly 80 injured in a stampede as thousands tried to enter a stadium venue.