Thailand’s projects under China’s Belt and Road Initiative are coming under scrutiny after a 7.7-magnitude earthquake in Myanmar destroyed a 30-story building that Chinese engineers were building in Bangkok, 966 kilometers (600 miles) away.

The only buildings to collapse in the lightly damaged Thai capital were incomplete skyscrapers. But the disaster caused substandard steel reinforcing bars to collapse, which turned the building into a huge pile of rubble, crushing about 87 construction workers, including 15 confirmed deaths and 72 missing.

“I have watched several clips of the building collapsing from different angles,” Thai Prime Minister Phaythan Shinawatra said.

“In my experience in the construction industry, I have never seen a problem like this.”

“We had to investigate thoroughly because a significant portion of the budget had been set aside and the completion deadline had been extended,” said Paytongtarn.

The investigation began with a strange, disturbing sight. Two days after the March 28 earthquake, four Chinese nationals were filmed running through the rubble, clutching as many construction-related documents as they could.

Police detained them, questioned them and released them. The Chinese embassy in Bangkok and Thailand’s powerful Interior Ministry, which oversees the police, met to discuss the collapse of the skyscraper, but their discussions were not made public.

China’s image is vital to Beijing’s reputation among Thais.

Washington and Beijing have been close allies for decades through financial aid, investment, tourism, education, traditional ties and other means. In Bangkok, they unofficially compete with each other for influence in diplomacy, politics, the economy and the military.

From the rubble of the collapsed skyscrapers, researchers extracted two types of steel reinforcing bars, also known as rebar, embedded in cement columns, which were supposed to be used to support the building.

After the earthquake, the Iron and Steel Institute of Thailand reportedly found that the rebar failed tests on their chemical composition, mass and tensile strength.

Photos released by the Ministry of Industry and local media showed a word embossed on a steel rebar dug up from the rubble.

The brand is said to be linked to a Chinese steel manufacturing company in Thailand, the Bangkok Post reported on April 2.