Quang Tri authorities have requested for assistance from central agencies in handling the case of 30 tons of frozen fish containing phenol, a harmful substance.
The province's chairman, Nguyen Duc Chinh, has sent an urgent letter to ask for help from the Ministry of Health, the Ministry of Science and Technology and the Vietnam Academy of Science and Technology, a source told Thanh Nien.
Last week, health inspectors found phenol in samples taken from a batch of 30 tons of frozen mackerel scads (Decapterus lajang).
The products were reportedly bought by the store's owner, Le Thi Thuoc, soon after fish in the central region began to die.
It was unclear how the scads, often caught around 15 kilometers offshore at 30 meters deep, were contaminated with phenol.
Phenol, or carbolic acid, is primarily used to synthesize plastics and related materials. The substance may cause harmful effects on the central nervous system, heart, liver and kidney, resulting in dysrhythmia, seizures and coma.
On Monday, health inspectors continued to take samples of frozen fish from other stores in the province for testing.
Officials said the discovery of phenol adds another blow to the region's fishing industry, already hit by a prolonged fish kill disaster.
In April, hundreds of tons of fish were washed ashore in Ha Tinh, Quang Binh, Quang Tri and Thua Thien-Hue provinces, apparently killed by industrial effluents.
Suspicion has centered on Hung Nghiep Formosa Steel Company, a major Taiwanese firm in the Vung Ang Economic Zone in Ha Tinh. The company admitted it has a large sewage pipe going straight into the sea, but it claimed all its discharged wastewater had been treated.
Officials are expected to disclose inspection findings this month.
According to some local fishermen, mackerel scads were not found among the dead fish in April.