Hundreds of people are missing and an unknown number believed dead after a partly constructed hydropower dam in southeast Laos collapsed, sending flash floods surging through six villages, state media reported Tuesday.
Communist Laos is traversed by a vast network of rivers and there are several dams being built or are planned in the impoverished and landlocked country, which exports most of its hydropower energy to neighboring countries like Thailand.
Laos News Agency said the accident happened on Monday evening at a dam in the country's far south, close to the border with Cambodia, releasing five billion cubic meters of water -- more than two million Olympic swimming pools.
The agency said there were "several human lives claimed, and several hundreds of people missing" while some 6,600 people had been made homeless as authorities scrambled to evacuate villagers from the devastation.
Aerial footage posted on the Facebook page of local news outlet ABC Laos showed a vast brown inundation swamping houses and jungle alike over a huge area.
Another video showed families waiting for rescue on the rooftop of their house, with a nearby Buddhist temple partially submerged.
Nearly 24 hours after the dam's collapse local authorities said they were struggling to gauge the extent of the disaster.
"We do not have any formal information yet about any casualties or how many are missing," an official in Attapeu province, where much of the flooding occurred, told AFP on condition of anonymity, adding that was "no phone signal" in the flooded region.
"We sent rescue teams who will help them and provide basic assistance first," the official added.
A Thai company involved in the hydropower project confirmed that a 770-meter long auxiliary dam used to divert river water had failed after heavy rainfall.
"The incident was caused by a continuous rainstorm which caused high volume of water to flow into the project's reservoir," Ratchaburi Electricity Generating Holding said in an English language statement.
The $1.2 billion dam is part of a project by Vientiane-based Xe Pian Xe Namnoy Power Company, or PNPC, a joint venture formed in 2012.
South Korea's Korea Western Power and the state-run Lao Holding State Enterprise are also involved in the joint venture.
The 410-megawatt capacity dam was supposed to start commercial operations by 2019, according to the venture's website.
The project consists of a series of dams over the Houay Makchanh, the Xe-Namnoy and the Xe-Pian rivers in Champasak Province.
It planned to export 90 percent of its electricity to energy-hungry Thailand and the remaining amount was to be offered up on the local grid.
Under the terms of construction, PNPC said it would operate and manage the power project for 27 years after commercial operations began.
'Battery of Asia'
Dam projects in Laos, mainly providing power to neighboring countries, have long been controversial with fears over environmental damage and the impact on communities who are often displaced to make way for the construction.
A massive hydroelectric project at Xayaburi, led by Thai group CH Karnchang, is at the heart of Laos' plan to become "the battery of Southeast Asia".
The 1,285-megawatt dam -- which will cost $3.5 billion according to state media -- has sharply divided downstream Mekong nations like Vietnam and Cambodia who worry it will disrupt vital ecosystems, fisheries and their own river systems.
Communist authorities in Laos keep tight control information and are often opaque about business deals and development projects. The media is state-controlled and the government vigorously pursues dissent or protesters.
The country has around 10 dams in operation, 10 to 20 under construction, and dozens more in planning stages.
"Once they cast themselves as the battery of Asia, exporting electricity became one of the major revenue sources, so it's basically selling natural resources such as water," Toshiyuki Doi, Senior Advisor at Mekong Watch, told AFP.
Occasionally reports of accidents in the hydropower sector do emerge.
Six Vietnamese workers were killed when a gas cylinder exploded at the construction site of a hydropower plant in central Laos in July last year.