A team from the Industry Ministry collected samples of the materials amid suspicions that their poor quality may have caused the collapse, said Pongpol Yodmuangcharoen, secretary of Minister Akanat Promphan.

Thai Deputy Prime Minister Anutin Charnvirakul, in charge of the rescue operation, confirmed an investigation to determine whether the design met seismic resistance standards.

He assured that both the Thai company Italian-Thai Development Plc and the Chinese subsidiary of China Railway No.10 Engineering Group, in charge of the construction, will be held responsible.

Police detained five Chinese nationals and one Thai interpreter for questioning after they were seen removing documents from the site, currently restricted to the public.

Thirty-seven files were seized from them for inspection.

The Ministry of Industry sued seven companies, Thai and foreign, for producing and selling deficient steel bars, which may have contributed to the collapse of the building.

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