Prime Minister Paetongtarn Shinawatra acknowledged that substandard steel may have been used in the construction of the State Audit Office (SAO) building that collapsed during the earthquake last Friday.
"Progress updates have been continuously reported, and the issue of [sub-standard] steel is one of the clearer aspects," she said on Thursday.
She said that the government's investigation has focused on the quality of steel used in the construction, with the Ministry of Industry inspecting various steel samples taken from the collapsed site.
Seven types of steel were tested, and initial findings revealed that there were two substandard ones -- 20mm and 32mm in thickness -- sourced from the same manufacturer, she said.
She then called for a meeting to be held either today or Monday to discuss the investigation into the deadly collapse further.
Industry Minister Akanat Promphan, meanwhile, confirmed that further inspections would be carried out in collaboration with a government-appointed fact-finding committee that includes members of the Department of Public Works and Town Planning, as well as the police.
This investigation will specifically target structural components and areas identified as potential causes of the collapse based on the contractor's blueprints, he said.
Separately, Teerajchai Phunthumas, an MP with the opposition People's Party and deputy chairman of the House Committee on Corruption and Misconduct Prevention and Suppression, has announced that the Auditor-General will be summoned on Thursday to clarify how compensation for the families of the victims of the collapse would be dispensed and explain the project's perceived bloated budget.
The official tally shows a total of 15 people have been confirmed dead, while scores of others are still missing.
Mr Teerajchai said that the Council of Engineers would be called upon to provide information on the materials and technologies used in the building's construction to help establish the cause of the collapse.
The Permanent Secretary of the Ministry of Industry will also be required to explain the procurement procedures, design and materials used, he said.
The SAO building's construction project, which was approved in 2020 with a budget of over 2 billion baht, was initially scheduled for completion in 2023 but faced delays of more than a year, he said.
The collapse has raised public concerns about why the building failed to withstand the earthquake impact despite the high budget, he noted.
