Hundreds of people are missing and an unspecified number are believed to be dead after the collapse of the Xepian-Xe Nam Noy hydroelectric dam in southeast Laos, state media reported on Tuesday.

The accident happened at a dam in southeastern Attapeu province late on Monday, releasing 5 billion cubic meters of water with "several human lives claimed, and several hundreds of people missing," the Laos News Agency said.

More than 6,600 people have been left homeless after their homes in the southern part of the district were swept away, the report said, and officials in the province have put out a call for relief aid for flood victims. Journalist Frederic Spohr, speaking with DW from Laos, called the event, "a major catastrophe for Laos and for the region."

Prime Minister Thongloun Sisoulith suspended meetings and led a delegation of cabinet members to the region to monitor events, the official Laos news agency KPL said.

ABC Laos reported that officials had brought boats to help evacuate people in San Sai district of Attapeu province, where the Xepian-Xe Nam Noy hydropower dam is located.

24-hour race to fix damage before collapse

The $1.2-billion (€1.02-billion) dam is part of a project by Vientiane-based Xe-Pian Xe-Namnoy Power Company, or PNPC, a joint venture formed in 2012. 

The Laos News Agency said the companies involved include Thailand's Ratchaburi Electricity Generating Holding, South Korea's Korea Western Power and the state-run Lao Holding State Enterprise. 

A South Korean builder also involved in the project, SK Engineering & Construction, said Wednesday that it had discovered Sunday evening that the upper part of the dam had been washed away. The discovery took place some 24 hours before the structure finally collapsed.

"We immediately alerted the authorities and began evacuating (nearby) villagers downstream," it said in a statement. Rain hampered repair work attempting to fix the damage.

Shares in SK's major shareholders fell sharply after the dam collapse.

The 410 megawatt capacity dam was due to start commercial operations by 2019, according to the project website.

It planned to export 90 percent of electricity generated to neighboring Thailand, with the remaining amount to be offered up on the local grid.

The 'battery of Asia'

The Xepian-Xe Nam Noy dam is part of Laos' massive plan to create a network of hydroelectric power plants. "Laos is not a manufacturing hub, it doesn't have skilled labor but what it has are hills and a lot of water. So the strategy was to kind of make Laos the battery of Asia," Spohr told DW. 

For years, critics such as the US-based International Rivers have warned of the negative impact such plans could have on the flora and fauna of the Mekong River as well as the villages of local residents who depend on them for their livlihood. Furthermore, they fear such plants will be unable to withstand increasingly extreme weather conditions like the series of five massive monsoons that battered the country in 2013, affecting some 347,000 Laotians.

Rivers International also pointed to the failings of Laos' warning system in this most recent event, saying: "This also shows the inadequacy of the warning systems for the dam construction and operations. The warning appeared to come very late and was ineffective in ensuring people had advance notice to ensure their safety and that of their families."   

js,law/rt (AFP, AP, Reuters)

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