TWO GEOLOGISTS were killed yesterday when a large rock, which had been loosened by an earlier explosion in a huge tunnel construction project in Chiang Mai province, fell on them.

The bodies of the victims – Prathomporn Siriwat and Pratchawat Wasu-anan, both 24 and from Chiang Mai – were taken to Mae Tang Hospital in Mae Tang district.

Wongpan Wongsamut, a chief engineer of the provincial irrigation office, said the accident took place after an explosion at a side tunnel, which is part of the Mae Ngad-Mae Kuang water-diversion tunnel.

He said the geologists were sent into the tunnel to examine the layers of stone when the loosened rock fell on them at about 7am.

“We are investigating the cause of the accident,” Wongpan said.

The project at Tambon Mae Horphra is now sealed pending the probe. It is part of a Bt11.5 billion, 23-kilometre tunnel project which is slated to be completed by 2021. Both men were working for Italian-Thai Development PCL on the site.

During a press conference yesterday, Noppadol Pianwet, a construction expert advising the project, said there had been a controlled explosion on Tuesday at the section of tunnel where the accident happened, which was buttressed by cement and bracing equipment.

The two geologists were sent to conduct an inspection for further tunnel drilling when the large rock, measuring about three-metres by one-metre, fell on them.

He dismissed speculation that the tunnel collapsed or rocks fell due to water pressure.

He said the project was located in a mountainous area and secondary faults would be normal. Workers at the site had already been trained on safety measures because rockslides were an anticipated risk.

He said the company would be extra careful and increase safety measures in the future, adding that the accident did not result from any flaws in the construction, design or bracing equipment.

Large Irrigation Construction Office 1 director Wit Wongkamonchun offered condolences to the families of the two men and said Bt50,000 funeral assistance money would be given to each family plus other compensation that could amount to at least Bt100,000.

Chiang Mai Provincial Labour Protection and Welfare Office safety inspection official Paksathorn Samitrapanya said her team was investigating the incident to determine if there were any occupational safety law violations.

Project engineer Sommai Buakham said officials assessed the area before the engineers entered the tunnel, adding that staff were required to wear safety gear.