The Criminal Court approved arrest warrants on Friday for five more suspects in relation to the deadly chemical leak that killed eight people at the Siam Commercial Bank headquarters.
The warrants were issued at the request of Phahon Yothin police who want to question more people responsible for the building and its fire prevention system.
One of them was Jeerawat Prempree, a structural engineer with Mega Planet Co, the main contractor for the fire extinguishing system upgrade at SCB Park. He reported to investigators at the station with his lawyer.
Others named are Somkid Tan-ngam, Somkid Chanhom, Treephob Youngprasertkul and Kajornjit Promdeeratch. Mr Treephob is a building manager with the property services company Jones Lang LaSalle, Miss Kajornjit works for Abit Multisystem Co, one of the firms subcontracted by Mega Planet to do the fire prevention upgrade work.
Jones Lang LaSalle manages the buildings at SCB Park.
Police earlier questioned Mega Planet managing director Napong Suksanugan and Adisorn Poda, a company director, who were later released on bail.
They were accused of violating contractual commitments to hire only experts and experienced workers to conduct maintenance of the fire protection equipment. However, they maintain they followed the proper standards.
The accident on Sunday night killed eight workers. Investigators have interrogated more than 30 witnesses so far but are still seeking more information.
Pol Lt Gen Sanit Mahathaworn, the acting Metropolitan Police Bureau chief, said investigators were waiting for additional evidence from forensic technicians before they can conclude the case.
Suchatvee Suwansawat, president of the Engineering Institute of Thailand, said he believed the workers did not die from lack of oxygen, as had been reported earlier.
Death probably resulted from inhaling small particles of condensed Pyrogen aerosol gas used by the fire extinguishing system for more than 15 minutes, he said. This affected their breathing, heart rates and blood circulation leading to their death, he added.
Staff from the institute inspected the scene on Monday.
