What caused the collapse of the Pearl River Bridge?

Crushing of steel pipe column. According to the inquiry of Pacific Auto, the workers illegally removed the steel pipe support at the bottom of the box girder of the Pearl River Bridge, which led to the collapse of the steel pipe column and the instability of the full-house support, leading to the collapse of the whole support system. Pearl River Bridge is a river-crossing bridge, located in Guangzhou, Guangdong Province, China, which is the first batch of historical buildings in Guangzhou. Construction started in June 1958+ 10/9, the main bridge project was completed in June 1960 and opened to traffic in June 1960.