Huynh Khanh Toan, vice chairman of the province People’s Committee, said flash floods triggered by Typhoon Rai caused the water tunnel at the Song Bung 2 Hydropower Plant to collapse when 18 workers were working nearby.
The two missing workers have been identified as Nguyen Minh Luan, 24, and Dang Van Tien, 36.
Rescuers are searching for all the missing people.
Zoram Huan, head of La Ee Commune in the province’s Nam Giang District, said three houses in his commune were washed away and many others were inundated.
Ten people in the commune are missing after the tunnel collapse.
A source told Thanh Nien that 12 people were working near the site and four are missing.
Lowland areas are trying to find out if more people are missing. Figures on material losses are not yet available.
In a report on the incident, Vuong Thanh Chung, deputy director of the hydropower plant management, said the tunnel collapsed because of severe flooding.
The two missing workers were operating dredging machines for the Hydraulics Construction Corporation No.4, he said.
“The other main parts [of the dam] are not damaged and are operating safely,” he said.
The reservoir began to collect water on September 25.
The 100-MW plant belongs to the Power Generation Corporation No.2 and has two turbines that generate more than 425 million KWh a year.