Villagers take refuge on a rooftop above flood waters from a collapsed dam in the Attapeu district, Laos, on Tuesday, July 24, 2018. Image Credit: AP

Bangkok: Hundreds of people are missing and an unknown number believed dead after the collapse of a hydropower dam under construction in southeast Laos, state media reported on Tuesday.

Several dams are being built or are planned in Laos, an impoverished and landlocked communist country that exports most of its hydropower energy to neighbouring countries like Thailand.

Laos News Agency said the accident happened at a hydropower dam in southeastern Attapeu province’s Sanamxay district late Monday, releasing five billion cubic metres of water — more than two million Olympic swimming pools.

People sitting on a rooftop of a house surrounded by floodwaters in Attapeu province after a dam collapsed the day before. AFP

The report added that the there were “several human lives claimed, and several hundreds of people missing.”

Several houses in the southern part of the district were also swept away, the report said, and officials in the province put out a call for relief aid for flood victims.

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.

Among the companies involved in the project according to the Laos News Agency are Thailand’s Ratchaburi Electricity Generating Holding, South Korea’s Korea Western Power and the state-run Lao Holding State Enterprise.

The 410 megawatt capacity dam was supposed to start commercial operations by 2019, according to the venture’s website.

The project planned to export 90 per cent of its electricity to energy hungry Thailand and the remaining amount was to be offered up on the local grid.