The Department of Special Investigation (DSI) will interrogate 40 engineers involved in the construction of the collapsed State Audit Office (SAO) building on Tuesday.
The interrogation is part of a probe into the unlawful use of nominees in the company that won the contract to build the doomed building, as well as the alleged bid rigging in the project.
The probe began last month, when DSI investigators seized stacks of documents stored in 24 storage containers that were used as temporary offices at the construction site in Chatuchak district.
According to DSI deputy director-general, Pol Capt Surawut Rangsai, investigators are focusing on documents which contain blueprints of the building, details of the jobs that were handled by China Railway No.10 (Thailand) Co (CREC) and its subcontractors, as well as the procurement of materials used in the project.
In total, 40 engineers will be summoned for questioning, said Pol Capt Surawut.
Investigators aim to finish questioning the engineers in four days, but that will depend on their cooperation, he said.
DSI spokesman Pol Maj Woranan Srilam said while the investigation on the use of nominees in CRECT is almost complete, authorities have yet to make any headways in their investigation into the bid rigging allegation.
Pol Capt Surawut said he was confident that documents thought to be crucial to the investigation had not been lost, despite reports of Chinese workers smuggling a bunch of documents out of the site shortly after the March 28 earthquake.
Those documents are now in the authorities' hands, as the workers who were seen taking the documents out were immediately taken into police custody, he said.
The documents will be examined by experts from the Department of Public Works and Town & Country Planning to ensure quicker progress, he said.
Meanwhile, the mission to recover bodies still trapped under the rubble continued on Monday.
According to Bangkok governor Chadchart Sittipunt, as of Sunday evening, rescue workers, aided by heavy machinery, have recovered 63 bodies, while 31 are still unaccounted for.
