Three people were killed by poisonous gas formed in a well in the Central Highlands province of Dak Lak Wednesday .
Le Van Dinh, 19, was killed first when he climbed down a 9-meter well in his back yard to fix the water pump.
His family asked a neighbor named Khanh, 20, to climb down after Dinh didn't return. But Khanh fainted and fell as he climbed down.
Hoang Van Phiem, another neighbor 39 years old, then climbed down the well and also ended up dead.
Two other rescuers named Cuong and Quy tied ropes around themselves and were pulled out of the well as soon as they fainted, local news website Vnexpress reported.
Four people in the northern province of Vinh Phuc, including a father and son, were killed in the same fashion in May.
According to experts, wells used by residents in rural and mountain areas are usually not cleaned properly and can accumulate a large amount of lethal methane gas.
Multiple deaths due to well gas have been reported in several regions recently.
In May last year, two people died similarly in the northern province of Lai Chau. Six people including rescuers were killed in the Central Highlands province of Gia Lai in April 2007 and four in the central province of Khanh Hoa in June 2005 under similar circumstances.