More than two dozen people have died in southeastern Laos after part of a newly built hydroelectric dam broke on July 23, flooding nearby villages. Government officials on July 25 said it had confirmed 26 deaths, with fears the death toll will rise with more than 130 people officially listed as missing and heavy rain continuing in the region.

Officials said more than 3,000 people lost their homes due to flooding after the dam broke on Monday. Social media posts showed people sitting on rooftops, with numerous boat rescues ongoing, and the heavy rain is hindering rescue efforts. The intergovernmental Mekong River Commission said rainstorms have caused water levels in the river to rise by as much as 15 feet in the past week.

The hydropower project is one of dozens under construction in Laos, many backed by Chinese companies, as the country seeks to provide more access to electricity for its population, a common thread in Southeast Asia. Khammany Inthirath, Laos’ minister of Energy and Mines, in a July 4 meeting told government officials about 92% of the country’s population has access to electricity, with a goal to reach 95% of Laotian households by 2020. The country also wants to increase its power exports to neighboring countries, including Thailand.

The failed dam is part of the Xe-Pian Xe-Namnoy hydroelectric project. The dam failed Monday evening during heavy rains, sending more than 170 billion cubic feet of water downstream. The project is being developed by two South Korean companies—Korea Western Power and SK Engineering & Construction (SK E&C).

Korea Western Power in a statement said one of five auxiliary earth-fill dams at the project was visibly weakened on July 20. SK E&C in a statement said the top of the dam collapsed July 22 despite efforts by workers to control the damage during heavy rain.

Water began flowing rapidly out of the reservoir on July 23. SK E&C said seven nearby villages were quickly flooded. The company said it was assisting evacuation and rescue efforts.

Thongloun Sisoulith, the country’s prime minister, at a July 25 news conference said some residents had been rescued from trees and confirmed several villages and farmland had been flooded. Bounhom Phommasane, governor of the district of Sanamxay, told The Vientiane Times newspaper, “A second step for us will be to recover and identify the deceased, but for now, we hurry to find those who are still alive in the area.”

Phon Vuongchonpu told Associated Press his family of 12 was safe but said, “The water came so quick we just left the house and ran away. We’ve lost everything: motorbike, furniture, our cows and pigs.”

The International Red Cross said it was working to send water purification units and food to the area. The office of South Korean President Moon Jae-in said the president had ordered an emergency relief team to Laos to help with recovery efforts.

The $1.02 billion Xe-Pian Xe-Namnoy project, designed to have 410 MW of generation, encompasses several river basins in a remote corner of southeastern Laos. It is the first hydroelectric dam to be built in Laos by a South Korean company and was due to come online in 2019, with 90% of its power exported to Thailand. Officials said the project was about 90% complete. Construction on the project began in 2013.

The project includes construction of three dams—Houay Makchan Dam, Xe Pian Dam, and Xe-Namnoy Dam—along the Mekong River. It also includes auxiliary, or saddle dams, including the Saddle Dam D that failed. The Xe-Pian Xe-Namnoy project includes a storage reservoir on the Xe Namnoy River, along with underground tunnels, shaft waterways, and an open-air powerhouse with four generator units: one Pelton turbine and three Francis turbines.

Laos’ energy plan calls for the operation of 100 hydropower plants with combined installed generation capacity of 28 GW and annual power output of about 77 TWh by 2020. The government has said about 85% of the hydropower output would be exported.

The Laos News Agency this month said the country currently operates 46 hydropower plants with combined generation capacity of 6,444 MW and annual power output of about 35 TWh. It reported there are 54 hydropower plants under construction across the country.

Laos is expanding its hydropower generation to take further advantage of the country’s plentiful water resources. The country has just one non-hydro facility, the 1,878-MW coal-fired Hongsa plant, which has operated since summer 2015. The plant was mostly financed and built by interests in Thailand, and nearly 90% of its power is exported to Thailand.

Laos also exports electricity to China and Vietnam, and is negotiating potential power exports to Cambodia and Myanmar.

Environmental advocates have expressed concern about the pace of construction of new plants along the Mekong River and its tributaries. International Rivers, a group that has been critical of such projects, in a statement said the disaster showed the need to improve warning systems around hydropower projects.

“With over 70 hydropower projects currently built, under construction and planned across Lao PDR—most of them owned and operated by private companies—authorities must immediately review how dams are being planned, designed and managed,” International Rivers said in a statement.

Darrell Proctor is a POWER associate editor (@DarrellProctor1, @POWERmagazine).