Chinese police have arrested a building owner and eight other people, two days after the structure collapsed, leaving dozens of people trapped or missing, police and state media said on Sunday.

The official Xinhua News Agency said the building’s owner was among the arrested.

Police in the city of Changsha said they had also arrested three people in charge of design and construction and five others for what they said was a false safety assessment for a guest house on the fourth to sixth floors.

Five people had been rescued by late on Saturday, more than 24 hours after the collapse. About 20 remained trapped, and another 39 have not been accounted for.

In photos the building appeared to have flattened down to about the second floor, leaving rubble strewn on the pavement. It had stood in a row of buildings about six storeys tall in Changsha, the capital of Hunan province.

Xinhua said the building had eight floors, including a restaurant on the second floor, a cafe on the third floor, and residences on the top two floors.

Other media reports said it was a six-storey building.

Tenants had made structural modifications to the building, but the cause of the collapse remains under investigation, Xinhua said.

Police said the Hunan Xiangda Engineering Testing Co issued the false safety report on April 13. Those arrested included the legal representative of the company and four technicians suspected of providing the assessment.

Following an increase in the number of collapses of self-built buildings in recent years, Chinese President Xi Jinping said on Saturday that it is necessary to check such structures for any hidden dangers and fix them to prevent major accidents, Xinhua said.

Poor adherence to safety standards, including the illegal addition of extra floors and failure to use reinforcing iron bars, is often blamed for such disasters.