On July 12, the Lai Chau Provincial Police began investigating the incident. The workers, Vu To S. (41 years old), Thao A T. (38), and Phung Lao U. (31), entered the Nam Cuoi 1 hydropower tunnel around midnight on July 11 to transport materials. They were overcome by gas approximately 1.2 km from the tunnel entrance.

Upon receiving the report, Colonel Nguyen Viet Giang, Director of the Lai Chau Provincial Police, directed relevant units to approach the scene and coordinate with the Nam Nhun District People's Committee to carry out rescue and relief measures.

By 8:30 AM, authorities had reached the tunnel entrance and began surveying and assessing the incident area. A reconnaissance team equipped with specialized protective gear entered the tunnel to search for the victims. At 10:32 AM, the team located the victims over 1.1 km from the tunnel entrance, with two found in the cabin of an excavator.

The reconnaissance team was ordered to withdraw from the tunnel and report for direct instructions from provincial leaders.

Upon learning of the incident, Colonel Le Anh Hung, Deputy Director of the Lai Chau Provincial Police, dispatched a task force of 16 officers and firefighters. This team coordinated with the related agencies, used specialized protective equipment to enter the area and conduct a forensic examination of the scene.

By 12:45 PM, the scene examination was completed, and the forces removed the three bodies from the tunnel, handing them over to the relevant authorities for further investigation. After the initial investigation, the bodies of the three victims were returned to their families on July 11.

According to the Lai Chau Provincial Portal, the Nam Cuoi 1 hydropower project is located on the Nam Cuoi stream, spanning the Nam Hang, Hua Bum, and Nam Pi communes in Nam Nhun District. The project is owned by Nam Cuoi 1 Hydropower Joint Stock Company and has an installed capacity of 19 MW.

Nhi Tien