The government will make public the cause of the mass fish death in central Vietnam in April Thursday afternoon, the information minister has said.
The "culprit" will be named at a press conference held by the Government Office in Hanoi, Minister of Information and Communications Truong Minh Tuan said.
The government would also explain why there has been a delay in revealing the cause and what steps it plans to take next, he said.
In what was described by the government as "unprecedented environmental pollution," tons of dead fish and other marine life washed up on central shores for around three weeks in April.
It devastated local fishing and hit tourism in the area.
Earlier this month the government said it had cracked the mystery and promised to reveal the cause within this month.
Tuan then said that the government agencies involved in investigating the incident needed more time to "collect not only scientific evidence but also legal evidence" against the culprit.
Vietnam invited experts from Germany, Japan, the US, and Israel to participate in the investigation.
Prime Minister Nguyen Xuan Phuc promised to "not shield anyone found causing the pollution."
Formosa Ha Tinh Steel Corp., a subsidiary of Taiwan’s Formosa Plastics, which is building a steel plant in the area where the fish died, was questioned.
The Ministry of Natural Resources and Environment said in late April, following a preliminary probe, that the fish deaths may have been caused by "toxins discharged by human activities" and algal blooms known as a red tide.
It said it had not found evidence of Formosa's culpability.
Many Vietnamese scientists, however, are not convinced.
Lawmakers in Taiwan earlier this month urged their government to investigate Formosa's possible role in the fish deaths in Vietnam.