BANGKOK, Thailand -- Several people died, hundreds were missing and
6,600 left homeless Tuesday (July 24) after a partially constructed
dam collapsed in southern Laos, dumping more than 1 billion gallons (5
billion liters) of churning water onto villages below, official
reports from the communist country said.

The collapse of the partially constructed hydroelectric dam on Monday
(July 23) night in Attapeu province was described as an accident
caused by heavy rain.

The 1 billion gallons (5 billion liters) of water which roared out
equals 2 million Olympic-sized swimming pools, according to one
report.

"The incident was caused by a continuous rainstorm which caused a high
volume of water to flow into the project's reservoir," the dam's
Thailand-based Ratchaburi Electricity Generating Holding reportedly
said in an English-language statement.

Rainwater "fractured" the "Saddle Dam D" and "leaked to the downstream
area," it said.

The dam's other investors include South Korea's Korea Western Power
and the Laos government's Lao Holding State Enterprise.

"Saddle Dam D" was described as 2,300 feet (770 meters) long, 53 feet
(16 meters) high, and 26 feet (8 meters) thick.

"We believe parts of the upper part of the dam were lost due to heavy
rainfall, and water overflowed from the supply dam," the British
Broadcasting Corp. (BBC) quoted a spokesman for South Korea's SK
Engineering & Construction which also invested in the dam.

Photographs from the scene showed distraught villagers clinging to any
available roof where the flood inundated homes and other buildings.

Victims also climbed onto floating objects, including boats used for
transport and fishing on the river.

Where water was less deep, long lines of people carrying whatever
belongings they could hold, waded toward higher ground.

In an aerial photo, the huge rural expanse of jungle and buildings
appeared like tiny dots in a brown soup amid clusters of trees -- as
far as they eye could see.

"The disaster has claimed several human lives, left hundreds of people
missing and more than 1,300 families -- 6,600 people -- homeless," the
government-run Lao News Agency said.

Flash floods hit at least six villages, the agency said.

Tons of gushing water also swept away an unknown number buildings as
it tumbled from the broken dam and flooded the valley along the
Boloven Plateau.

Sanamxay district where the collapse occurred is about half-way
between Thailand and Vietnam, and close to the Laos-Cambodia border.

Lao Prime Minister Thongloun Sisoulith led his cabinet and other
senior officials to Sanamxay on Tuesday (July 24) to monitor rescue
and relief efforts, the Lao News Agency said.

"Authorities of Attapeu Province have urged the [Communist] Party,
government organizations, business community, officials, police and
military forces and people of all strata to provide emergency aid for
the victims of the disaster, namely: clothing, food items, drinking
water, medicines, cash and other relief items," the Lao News Agency
said.

U.S. warplanes dumped more than 2 million tons of bombs on Laos --
equal to about 1 ton of explosives for every person -- between 1964
and 1973 during the region's Vietnam War.

After the communists achieved victory in 1975, their regime limped
along supported by U.S. and other international aid, plus investment
by foreigners hoping to cash in on the country's rich natural
resources.

Impoverished Laos has been constructing several hydroelectric dams
along its rivers, to become "the battery of Southeast Asia" and sell
the electricity to neighboring countries.

Laos is lightly populated and has very little infrastructure, so it
would need only 10 percent of the electricity from the stricken
project.

The other 90 percent was to be sold to rapidly modernizing Thailand
which is also dependent on neighboring Myanmar -- mostly for Bangkok's
increasing power needs.

The mass of water which cascaded down from the dam immediately flooded
the Xe Pian River below which flows south before crossing into
Cambodia where it becomes a tributary of the larger Mekong River.

The $1.2 billion dam project is operated by Xe Pian Xe Namnoy Power
Company (PNPC) based in Vientiane, the capital of Laos, as a
multinational venture agreed upon in 2012, according to the French
news agency Agence-France Presse.

The dam was to offer electricity for sale starting in 2019, AFP said.

Lao officials described the collapsed site as a "saddle dam" also
known as an auxiliary or subsidiary dam, which contains water that has
been diverted after the main dam reservoir overflows.

"A saddle dam is a dike or a wall built at the edge of a lake or
reservoir to protect nearby land from flooding," said Antonya Nelson,
an American writing on the website Home Ground which describes
landscape terminology.

"The name derives from the low dip in the landscape -- or saddle --
across which the dam is constructed. All four dams at Horsetooth
Reservoir in Colorado are saddle dams," Mr. Nelson wrote.

Power-technology.com which reports on the global energy industry said
a saddle dam "is used to hold water beyond what is held by the main
body of the dam."