Thai authorities probe materials and construction practices after deadly building failure.

Thai investigators have discovered that the collapsed State Audit Office tower in Bangkok, which crumbled during the 28 March earthquake, contained substandard steel sourced from a factory previously shut down by authorities.

Tests conducted by the Iron and Steel Institute of Thailand found that steel bars recovered from the wreckage failed to meet required standards for mass, chemical composition, and durability. The materials were traced back to Xin Ke Yuan Steel, whose factory in Rayong province was ordered to cease operations in December following a gas leak incident. Officials had already seized over 2,400 tonnes of steel from the company.

The 30-storey structure was the only building in Bangkok to suffer complete failure in the aftermath of the 7.7-magnitude earthquake in Myanmar. The collapse left at least a dozen workers dead and nearly 80 trapped. The shocking incident has prompted a separate government-led inquiry into construction failures.

The tower was being built by ITD-CREC, a joint venture between Italian-Thai Development and China Railway Number 10 Thailand. Investigators will examine whether the Chinese firm used Thai proxy shareholders to bypass local ownership laws. Meanwhile, further steel samples will be tested as part of the broader investigation.

Authorities have vowed to take action against those responsible, with Industry Minister Akanat Promphan confirming that legal measures will be enforced under Thailand’s Industrial Products Standards Act. Officials will also inspect Xin Ke Yuan Steel’s inventory to ensure compliance with shutdown orders.

The dramatic collapse, widely shared in viral images, has intensified scrutiny over Thailand’s construction standards. While Bangkok largely withstood the earthquake’s impact, Myanmar suffered catastrophic destruction, with over 2,000 fatalities reported near the epicentre.