The collapse of a skyscraper under construction in Bangkok — the lone building to crash during the massive earthquake last week — has become the center of Thai investigations as questions swirl around the construction and quality of the materials used by a joint venture of Thai-Chinese contractors.

The 30-story building, which was set to be a new location for Thailand’s State Audit Office, crumbled within minutes of the 7.7-magnitude earthquake, killing 11 workers and trapping nearly 80 people. Last-ditch efforts are ongoing to find survivors, with the massive piles of concrete rubble making the task difficult even after 72 hours of the quake.

Thailand’s Interior Minister Anutin Charnvirakul on Sunday set up a panel of experts to probe the collapse and report its findings to the government within seven days. Separately, the Ministry of Industry has collected samples of steel bars found at the site to test the quality of the material.

The top of the building, which was about 45% complete, was seen crumbling first, before the entire structure came down, sending rubble and debris flying everywhere. Bystanders were heard screaming in disbelief in the videos that went viral on social media.

“We’ve never seen anything like this in Thailand,” said Suchatvee Suwansawat, a civil engineer who ran for Bangkok governor during the 2022 election, at the site of the collapse on Sunday. “The way it collapsed, like there was an explosion, isn’t normal. The question is how do we identify the abnormality to find the cause?”

While the contractors haven’t offered any explanation yet for the collapse, Italian-Thai said it was committed to “taking corrective actions to restore normalcy as soon as possible.” The company, one of the biggest Thai contractors, was in the news last year as it faced a cash crunch and frequent accidents at some of its project sites. It was also under fire earlier this month for the collapse of an under-construction highway in Bangkok which killed six people.

China Railway Number 10 couldn’t immediately be reached for comment. The firm is a subsidiary of state-owned China Railway Group Ltd.. The joint venture with Italian-Thai was also listed as a contractor for one part of the Thailand-China high-speed railway project, according to a government website.

Chinese Support

As the companies drew heat, China’s ambassador to Thailand Han Zhiqiang met with minister Anutin and pledged to support the government in its investigation, the minister said.

The probe will focus on the designer, construction supervisor and contractor, Anutin said. “If it’s proven that the builder strayed from the design plan and used other material than what was specified, they will be punished under the law,” he told reporters.

Although Myanmar was hit much worse, with the death toll set to climb from more than 1,700, the incident in Bangkok stood out in a city that withstood much of the impact of the temblor. About 13,000 buildings have reported some form of damage to Bangkok authorities, according to Thanes Weerasiri, president of the Council of Engineers Thailand. Only two of them were categorized as critical, while about 2,000 others still needed pection, Thanes said on Monday.

Shares of Italian-Thai tumbled as much as 27% in Bangkok trading, the most in a year. The collapsed building has insurance coverage for the full contract value, the company said, adding that it will provide compensation and relief for the families of those killed and medical care for injured survivors.

Shares of several condominium builders were hit on speculation that buyers may prefer landed houses to high-rise residential towers in Bangkok, among the world’s top tourist destinations. The Thai property development index tumbled as much as 4.3%, with Everland Pcl, AP Thailand Pcl and Origin Property Pcl among the biggest losers.

Photograph: Rescue workers search for survivors in the rubble of a building that collapsed following an earthquake in Bangkok on March 29, 2025; Photo credit: Andre Malerba/Bloomberg

Copyright 2025 Bloomberg.