As the search for the two workers, Prai Khanoonram, 38, and Boonjaeng Lesla-ong, 46, continued yesterday, rescuers requested the use of military sonar cameras to aid the operation, while relatives anxiously awaited for news of their loved ones.

City officials and engineering experts met yesterday to discuss the situation.

Council of Engineers secretary-general Amorn Pimanmas said that since the building on Sukhumvit Soi 87 was higher than three storeys, the demolition job needed to be supervised by engineers.

He said because the building was a flat-slab structure with more beams than pillars and required slings to hold parts of the structure in place and handle its weight, the failure to thoroughly study the structure before its demolition could be problematic.

Amorn said that tearing down the building required a proper collapse-preventing brace system but the initial inspection found the demolition had used an incorrect brace system.

He said experts would look at the steps taken and the tools used in the demolition as well as launch an ethical probe against those involved in the job.

The permanent secretary for the Bangkok Metropolitan Administration, Paparut Dardarananda, said the urgent mission was to find the missing workers while ensuring rescuers’ safety because a building next to the site had been affected by the demolition and could collapse.

With slings being used to hold structures in place, rescuers yesterday shifted from using a crane to remove the toppled concrete slabs to drilling through one slab at a time and slipping a camera through the holes to search for the workers. The drilling was done at spots identified by sniffer dogs.

“From now on, the BMA will get involved more in ensuring the building demolition companies’ professional practices, as problems that have led to tragedies might stem from the contractors’ inexperience or a misunderstanding,” he added.

Thanes Weerasiri, acting president of the Engineering Institute of Thailand, said the institute would set up a volunteer engineering unit to aid related agencies in providing knowledge on how to best aid people trapped in collapsed buildings so rescuers could identify unsafe spots.