A report by China's Cabinet says 53 people are in custody in an investigation into a landslide that killed 73 people and left four others missing in the southern city of Shenzhen last year.

The State Council's investigation report said Friday the landslide in which a mountain of construction waste that had been piled up against a hill collapsed during heavy rains onto an industrial park was an "extraordinarily serious production safety accident."

The report said the Dec. 20 landslide destroyed 33 buildings and resulted in "direct economic losses" of $132 million.

Shenzhen is a major manufacturing center, making everything from cellphones to cars, and it attracts workers from all parts of China.