Thailand's interior minister has demanded findings from a probe into the collapse of the Chinese-constructed State Audit Office building within seven days as four Chinese workers were questioned for snatching documents from the area.

China has sent an expert to inspect the collapse site.

Interior Minister Anutin Charnvirakul said on Sunday that a committee is expected to conclude the probe in seven days.

The committee has experienced engineers from the Department of Public Works and Town & Country Planning and experts, he said.

“Thailand will quickly find out why the building collapsed. It was just built and should have been designed to withstand earthquakes,” the interior minister said.

He referred to the 30-storey building that was to be the new headquarters of the State Audit Office in Chatuchak district of Bangkok. The State Audit Office contracted a consortium of Italian-Thai Development Plc and China Railway No.10 Engineering Group to construct the 2.1-billion-baht building.

The investigation would focus on architects, construction supervisors and builders, Mr Anutin said. The Thai and Chinese partners in the construction consortium would have to share responsibility. 

He also said that rescuers were trying to reach trapped victims as soon as possible.

Meanwhile, police questioned four Chinese men who took 32 files from containers behind the collapsed building.

The four men worked for a company that was a part of the consortium of Italian-Thai Development, he said.

According to the deputy Bangkok police chief, the files contained various documents including information about contractors and sub-contractors. Police seized the documents.

The Chinese men told police that they gathered the documents to prepare insurance compensation claims. The Chatuchak district office would file a complaint against them.

Meanwhile, Bangkok governor Chadchart Sittipunt asked the owners of big buildings, theatres, hotels, billboards and plants to check their building strength and safety within two weeks.