Hanoi Environmental Police confirmed waste water from Ciputra, a modern apartment complex developed by Indonesia's Ciputra Group, was not treated.

Captain Le Quang Minh, from Hanoi Environmental Police, said Ciputra's investors tried to delay the construction of a waste treatment system, claiming it had encountered problems securing land used by the village as a cemetery for the task.

"We can only fine the investors for discharging into the environment," Minh said. "The situation hasn't gotten better for many years."

Le Van Duc, director of the Hanoi Department of Construction, said the city has more than 150 apartment complexes grouping thousands of buildings, but few have waste treatment systems.

He said investors saw no value in building treatment systems that did not generate additional income, while Vietnam lacks any regulatory clout to punish violators. The fine of VND2bn (USD95,200) for enterprises and VND1bn for individuals are considered too light. But a lack of inspectors and necessary testing equipment meant only a few cases were being pursued.

In 2012, residents in Ciputra complained that water from building sewers and toilets was overflowing in their apartments.

"We paid a high prices for the apartments and a VND10m service fee," one Ciputra resident said. "It's unacceptable that investors can't build a waste water treatment system. This has affected the lives of the complex's residents and people living nearby."

A leader of Song Da-Thang Long JSC., a major investor in the Van Khe apartment complex in Ha Dong District, said the development did not have a waste treatment system because the technology and equipment was expensive.

Experts say 40 percent of the city's water is sourced from groundwater, and untreated waste discharged from apartment complexes creates a worsening pollution problem.

"Investors should include the environmental price when they sell the apartments," said Tran Hieu Nhue, head of the Institute for Water Engineering and Environmental Technology.

"The waste water may not have immediate effect, but it will lead to severe consequences," Nhue said. "In the worst case, the waste water is being directly discharged into the environment and contaminates groundwater."