Workers cover the burned area of Rang Dong Light Source and Vacuum Flask JSC in Thanh Xuan Trung Ward, Thanh Xuan District, Hanoi. September 4, 2019. Photo by VnExpress/Tat Dinh.

The Rang Dong Light Source and Vacuum Flask JSC, whose warehouse had caught fire last week, had reported that over 15 kilograms of mercury have been released into the air since, but scientists estimate the actual figure could reach over 27 kilograms, the Ministry of Natural Resources and Environment said at a press conference Wednesday.

Test results show that between August 30 and September 1, within a 200-meters radius of the warehouse fire, mercury levels were at an alarm level that would adversely impact people’s health under World Health Organization (WHO) standards.

Inside the warehouse area, the mercury level exceeded WHO warning levels by 10-30 times, which means it would have very bad effects on people’s health, officials said at the conference.

12 out of 13 sediment samples at a location one kilometer away from the company’s discharge drain recorded mercury levels exceeding the safety limit by 6.1 times.

"The Rang Dong fire has inflicted big damage on assets and has had negative effects on nearby residents and environment," Deputy Minister of Natural Resources and Environment Vo Tuan Nhan said at the conference.

The environment ministry has asked the company to cover the burned area and reduce the release of mercury into the environment.

The Vietnam Academy of Science and Technology will cooperate with Japanese experts to continue measuring the release of mercury in the area of the fire, Nhan said.

For the long-term, factories with high risks of polluting the environment, like Rang Dong, need to be moved out of residential areas to prevent recurrence of such an event, he added.

A five-hour blaze that started at 6 p.m. last Wednesday destroyed a third of the inventory at a 6,000-square-meter warehouse belonging to Rang Dong in Thanh Xuan Trung Ward, next to Ha Dinh Ward, in the southwestern Thanh Xuan District. The inventory included light bulbs.

Residents near the fire in the following day started evacuating from their homes due to health concerns. Several reported fatigue and stinging of eyes.

Rang Dong, a leading manufacturer of lighting products and equipment, has estimated loss from the fire at VN150 billion ($6.4 million).

The police are investigating the fire and are yet to ascertain its cause.