CHIANG RAI, Thailand — Two construction workers were killed and three others sustained serious injuries on Saturday after a heavy installation component detached and fell onto them inside a major railway tunnel under construction in Chiang Rai province.

Train tunnel being built in Nakhon Ratchasima collapses, trapping 3

The fatal accident occurred inside the 3.4-kilometer Doi Luang Tunnel, a critical infrastructure segment of the State Railway of Thailand’s Den Chai–Chiang Rai–Chiang Khong railway project. The massive infrastructure initiative is designed to connect Den Chai district in Phrae province with the border district of Chiang Khong in Chiang Rai province, significantly enhancing regional connectivity and freight transport.

Preliminary reports indicate that the victims were working on a scaffold inside the tunnel, engaged in the installation of equipment believed to be part of the facility’s internal lighting system. During the operation, a heavy metal installation component—comprising circular steel rings connected by metal ribs—suddenly detached from the upper section of the tunnel. The massive structure plummeted onto the workers below, striking them and trapping the victims against the tunnel’s steel framework.

Emergency medical services and rescue teams were immediately dispatched to the site. Ambulances were able to navigate directly into the tunnel to reach the accident location, where specialized rescue personnel worked to extract the trapped individuals from the wreckage. The two workers who were struck by the falling component were pronounced dead at the scene, while the three others who suffered severe trauma were rapidly transported to a nearby hospital for urgent medical treatment.

Two Killed in Doi Luang Tunnel Collapse as SRT Orders Safety Review

The State Railway of Thailand (SRT) has expressed its condolences following a fatal accident at the Doi Luang Tunnel construction site on the Den Chai-Chiang Rai-Chiang Khong railway project.

The collapse… pic.twitter.com/5ONpD0TWcl

— Thai Train Guide (@ThaiTrainGuide) June 21, 2026

Initial site investigations revealed that the primary excavation phase for the Doi Luang Tunnel had already been completed. The tunnel’s structural integrity had been reinforced with a sprayed concrete lining, and extensive steel framework and scaffolding had been erected along the length of the passage to support the ongoing installation and finishing work.

Law enforcement officials and occupational safety inspectors have launched a comprehensive investigation to determine the exact cause of the structural failure that led to the collapse of the heavy metal component. The probe will focus on the installation procedures, the securing mechanisms of the steel rings, and the overall safety protocols in place at the time of the incident.

Myanmar Worker Dies in Bangkok Cable Tunnel Collapse

As the State Railway of Thailand and relevant construction authorities manage the aftermath of the tragedy, work at the site has been paused to facilitate the ongoing forensic and safety investigations.

-Thailand News (TN)