More than 2,000 residents living in a radius of 500 meters around the Rang Dong light bulb warehouse, which was destroyed by a fire late last month, are receiving free health checks.

So far, around 1,000 have been found to have mercury amounts at permitted levels in their blood.

"After seven days of checking, we have not found any sign of abnormal, acute poisoning," said Tran Thi Nhi Ha, deputy head of Hanoi's Health Department.

The five-hour blaze that started at 6 p.m. on August 28 destroyed a third of the inventory at the 6,000-square-meter warehouse belonging to the Rang Dong Light Source and Vacuum Flask JSC in Thanh Xuan District.

About 15.2-27.2 kilograms of mercury had been released into the environment following the fire, the Vietnam Environment Administration had said last Sunday.

Investigators have said that inadequate storage procedures were the cause of the fire. The exact cause is yet to be determined.

People living nearby have been moving out of their homes due to health concerns.

The municipal health department has been working with the education department in Thanh Xuan District to provide free health check for students at two schools, one primary and the other secondary, near the warehouse.

Minister of Natural Resources and Environment Tran Hong Ha said Thursday that areas surrounding the blaze-gutted Rang Dong warehouse are safe now.

Authorities have decontaminated polluted areas, he said, adding that materials left behind in the warehouse must be dealt with properly.

But Professor Jozef Pacyna of the AGH University of Science and Technology in Poland said a map detailing the areas affected by the mercury released from the fire is needed, as it might take several months or years before the element could become toxic.

Mercury by itself would not immediately have an impact on human health, Pacyna told VnExpress. The mercury released in the fire was inorganic, and it is its organic form that is toxic, he said, adding that the element could become toxic after it got absorbed in the soil and water and contaminate food sources like seafood.

Authorities have deployed both army and civilian personnel to decontaminate areas surrounding the Rang Dong warehouse Thursday.

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