District office director Apirom Chandrakul, who inspected the scene along with related officials yesterday morning, said the building was being modified. He added that he suspects the collapse could be blamed on the contractor’s lack of experience.

The work was legally permitted and was being done following required regulations, he said. It was due to be completed in a year.

Apirom said that while Lat Phrao Police Station officers would check to see if there was any recklessness, the district office and the BMA Public Works department would investigate further to see if the construction was being done according to standards.

The site will be sealed for up to 30 days pending the investigation, he said.

After the 6.30pm incident, crane truck driver Songto Khosila, 50, told police that he and other workers were installing a ready-made concrete floor when the floor and a beam collapsed on the workers.

The front of this two-storey house was being modified to become a four-storey structure.