Hundreds of people went missing with many believed drowned after a hydropower dam in Attapeu province of Laos collapsed late Monday, unleashing about five billion cubic metres of water downstream, flooding six villages.

A statement issued by the Laotian government in Vientiane via state media said that “several human lives” were lost and “several hundreds of people missing” after the hydroelectric dam in Attapeu province collapsed at about 8 pm Monday.

It added that more than 6,000 people have been left homeless by the ensuing flooding.

On Tuesday, the Lao government declared Sanamxay district in Attapeu province a national disaster zone and designated the Ministry of Labour and Social Welfare, the National Defence Ministry as well as all parties concerned to coordinate and mobilize resources for relief efforts.

According to BBC, construction of the Xe-Pian Xe-Namnoy dam began in 2013 and it was due to become operational next year.

The main Thai stakeholder in the project, Ratchaburi Electricity Generating Holding said it had re

ceived a report from the team’s operator that a “saddle dam” measuring 770 metres long and 16m high had collapsed.

It said continuous rainstorms had led a high volume of water to flow into the reservoir.

Currently, Xe-Pian Xe-Namnoy Power Company and related agencies have evacuated people

who live around the area, said the statement.

A spokesman for SK Engineering & Construction, a South Korean company with a stake in the project told the BBC a small supply dam – not the main dam – had collapsed due to unexpected heavy rainfall.

Prime Minister Thongloun Sisoulith has postponed government meetings and gone to the

affected area in Sanamxay district with senior officials to monitor

relief efforts, said the state media.