Hungarian authorities have ordered the evacuation of the village worst hit by the toxic sludge after damage was found in a wall of the reservoir that burst on Monday.
Kolontar is one of the places most affected by the spill from the reservoir of an alumina plant in Ajka.
Authorities say the damage to the northern wall of the reservoir is minor, but 800 villagers were evacuated early on Saturday as a precaution, the BBC reports.
The neighbouring village of Devecser could also be evacuated.
At least seven people have died as a result of the accident and about 150 people injured when up to 700,000 cubic metres of red toxic sludge flooded from the burst reservoir in western Hungary.
Residents and emergency workers have worked tirelessly to remove the worst of the sludge which has damaged houses, streets, farmland and polluted waterways.
All life in the Marcal River, which feeds the Danube, is said to have been extinguished.
On Friday, Hungarian Prime Minister Viktor Oben said the River Danube was no longer under threat of widespread pollution, easing fears that Europe's second longest river would be significantly polluted.
The European Union has been asked for urgent help in dealing with the disaster.