Vietnam will only allow Taiwanese conglomerate Formosa Plastics' local unit to dispose of waste once it is completely sure it can do so safely, the government said on Wednesday.
Formosa Ha Tinh Steel, which runs an $11 billion steel plant, polluted more than 200 km (125 miles) of coastline in April 2016, killing more than 100 tons of fish and devastating the environment, jobs and economies of four provinces.
The plant is current suspended from operating while the company seeks to address more than 50 violations identified by the government.
A statement on the government's website said it would only allow the firm to dispose of waste once it "ensures complete environmental safety."
It did not say how far the steel plant was from achieving that.
The company agreed to pay $500 million in compensation for the disaster. The environment ministry says complete recovery from the accident will take a decade.