Officials said the die-off has affected multiple aquaculture areas, particularly zones previously associated with Nam Thinh Commune in the former Thai Binh Province.
Preliminary data from the Nam Cuong People’s Committee showed the hardest-hit farms lost as much as 80 per cent of their stock, while others reported losses of around 20 per cent.
Authorities have worked with the provincial Sub-Department of Seas and Fisheries to collect samples and determine the cause of the mass deaths.
According to local residents, the losses may be linked to weather conditions, with low tides exposing clams to intense heat, potentially causing salinity or thermal shock.