VIENTIANE, July 24 (Xinhua) -- An under-construction hydropower dam collapsed on Monday in Sanamxay district of Laos' southeastern Attapeu Province, the provincial administration office announced in a statement on Tuesday.

The Xepian-Xe Nam Noy hydropower dam collapsed at 20:00 p.m. local time on Monday, releasing 5 billion cubic meters of waters, sweeping away several houses, claiming several human lives and leaving hundreds of people missing, said the statement.

The Attapeu Provincial Administration Office has announced relief aid for flood victims. Authorities of Attapeu Province also called on Party, government organizations, business community, officials, police and military forces and the Lao people to provide emergency aid for the victims.

Being constructed by Xe Pian-Xe Namnoy Power Company (PNPC), a joint venture of South Korean, Thai and Lao companies, the Xe Pian-Xe Namnoy hydroelectric power project is estimated to coast 1.02 billion U.S. dollars, and is estimated to have an annual electricity generation of approximately 1,860 GWh.

Feasibility study for the hydroelectric project was completed in November 2008. Construction of the project began in February 2013 and commercial operations are expected to begin in 2018.