The chemical division of the Vietnamese People’s Army has been monitoring areas around the warehouse since Thursday and spraying chemicals to prevent mercury from spreading.

Dozens of tons still need to be collected, authorities said.

A 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 Hanoi's Thanh Xuan District. An estimated 15.2-27.2 kilograms of mercury were released into the environment.

The five tons of toxic waste the military collected would be kept inside the warehouse until further instructions, a representative of the Urban Environment Company Urenco 10, which is helping with the decontamination, said.

Over 130 army and civilian personnel have been working since Thursday at the site.

But the cleanup is expected to take "a long time," said Nguyen Van Bong, head of the Hanoi City High Command’s search and rescue department.

Investigators have said poor storage procedures were the cause of the fire, but the exact cause is yet to be determined.

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

City authorities said no one in the area has tested positive for mercury poisoning yet.

Areas surrounding the gutted warehouse are now "safe," Minister of Natural Resources and Environment Tran Hong Ha stated Thursday.

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