NANNING, May 21 (Xinhua) -- At least four people were killed and 87 others injured as of 9 a.m. Tuesday after the roof of a night bar collapsed Monday in the city of Baise, southern China's Guangxi Zhuang Autonomous Region.

The injured are in stable condition, according to the regional emergency management department.

A total of 23 people have been summoned by local police for investigation and seven have been detained on suspicion of causing a major safety accident.

Local police and fire departments sent around 260 people to aid in search and rescue after the collapse occurred.

Both the national and regional health commissions sent medical expert teams to guide treatment of the injured on site.

The bar, with an area of 700 square meters, is located on the top floor of a three-story steel-framed building.

Investigation and clean up efforts are still underway. An overhaul on the safety of public areas and the building industry has been launched in Guangxi to avoid similar accidents.