BANGKOK — The head of the labor welfare department is threatening legal action against Italian-Thai Development Co. Ltd. after three workers were killed Friday night while working on the elevated Red Line extension.

The three fell and were killed in front of Wat Don Mueang school on Kamphaeng Phet 6 Road, when large metal beams used to support construction of a concrete cross support collapsed and fell to the ground at about 8:30pm.

“If the latest incident is an accident, we’ll file criminal charges against the construction company and make them improve their operation within a period of time,” said Sumet Mahosot of the Labor Protection and Welfare Department. “If they fail to do so, we’ll have to shut down the company.”

The president of Thailand’s Engineering Institute said the accident happened when several of the massive metal beams failed.

“T-bar beams that were securing metal beams to the concrete columns sheared,” Thanes Weerasiri said Saturday morning.

Thanes faulted the workers for inadvertently causing the beams to shear.

Sumet described it as the latest in a series of accidents.

“This is the sixth incident, with eight deaths for construction of the Red Line,” he said.

The area is currently closed for investigation and the fallen beams are expected to be removed by Tuesday.

Several accidents have occurred during construction of the Red Line. In 2015, a Italian-Thai construction crane collapsed and crushed two cars in front of Don Muang Railway Station in 2015, injuring one.