Transport Minister Arkhom Termpittayapaisith has suspended the construction of the Red Line elevated rail after a steel support structure fell off a pillar, killing three workers at a construction site near Wat Don Muang school.
Mr Arkhom has demanded construction company Italian-Thai Development Plc (Italthai) show responsibility and come up with a better plan in seven days to prevent a recurrence of the incident in the 21-billion-baht electric railway project, which has so far encountered six similar incidents and claimed eight lives in total.
The latest three victims -- Maitri Suphasiwat, Sangat Thepsanthat and Santiphong Sae Wang -- who were working on the structure, fell from the structure on Friday night, according to police and labour officials who inspected the spot.
The minister yesterday also suspended an engineer overseeing the project and set up a panel to ascertain the cause of the tragedy.
If it is found Italthai was at fault, the company will be blacklisted, permanent secretary for transport Chartchai Tipsunave said.
However, an initial inspection by the Engineering Institute of Thailand (EIT) could not confirm that carelessness was the cause.
The institute found a problem in one of six steel structures, called support launchers, which were attached to the pillars of the elevated rail track. One of them was torn by a "severe cut", causing the structure to fall, said EIT chairman Thanet Wirasiri.
Further inspection of the support launcher in a laboratory is needed in order to ascertain the nature of the damage, he said, adding that the other five support launchers also need to be examined for damage.
The company is required to work under safety guidelines to avoid accidents. An initial inspection found it followed the guidelines, but a mistake still occurred, Mr Thanet said.
The company sealed off the construction site and worked at night in order to avoid minimise the impact on local residents. However, it was probably "not convenient" to work at that time, which may have exposed workers to danger, said Mr Thanet.
Authorities have sealed off the area where the steel structure fell, pending further investigation into the incident.
Traffic in the area on part of Kamphaeng Phet 6 Road is expected to open on May 2, Mr Thanet said.
The Red Line is among the electric railway projects overseen by the State Railway of Thailand, which in 2013 hired Italthai to build the 20km-rail track linking Rangsit and Bang Sue.