Police in the central region's Quang Nam Province late last month arrested three people involved in the trafficking of 1.2 tons of cyanide.
The cyanide was being transported in 24 sacks on a truck.
Initial investigations show that Le Minh Tien, 37, had hired Luu The Long, 31, and Nguyen Cong Minh, 17, to deliver the deadly chemical compound.
All three of them, all locals, escaped when the truck was caught on November 29.
Unofficial statistics provided by authorities indicate that illicit gold miners in the mountainous regions of Quang Nam use up thousands of tons of cyanide every year.
Early last month, the province's police seized a vehicle containing more than three tons of cyanide, the biggest trafficking case of cyanide ever busted in Vietnam.
In May, police in neighboring Da Nang found two tons of cyanide on a bus bound for Quang Nam.
The chemical is used in gold mining to separate the precious metal from other substances.
The compound severely pollutes streams around the mines and poses a serious health hazard.