Emergency workers are trying to stop the spill, from an alumina plant, from flowing into major waterways, including the River Danube
A state of emergency has been declared in three western counties after the chemical waste burst from a reservoir.
Four people are known to have died, and 120 were injured. Six more are missing.
At least seven villages and towns are affected including Devecser, where the torrent was 2m (6.5ft) deep.
The flood swept cars from roads and damaged bridges and houses, forcing the evacuation of hundreds of residents.
The sludge - a mixture of water and mining waste containing heavy metals - is considered hazardous, according to Hungary's National Directorate General for Disaster Management (NDGDM).
While the cause of the deaths has not yet been officially established, the victims are thought to have drowned.'Desperate effort'
Some 600,000-700,000 cubic metres (21m-24m cubic feet) of sludge escaped from the plant, 160km (100 miles) from the capital, Budapest, affecting an area of 40 sq km (15.4 sq miles).
Environment Minister Zoltan Illes told the BBC the clean-up would take at least one year and probably require technical and financial assistance from the European Union.
He described the spill as Hungary's worst chemical accident.
in BBC World
A state of emergency has been declared in three western counties after the chemical waste burst from a reservoir.
Four people are known to have died, and 120 were injured. Six more are missing.
At least seven villages and towns are affected including Devecser, where the torrent was 2m (6.5ft) deep.
The flood swept cars from roads and damaged bridges and houses, forcing the evacuation of hundreds of residents.
The sludge - a mixture of water and mining waste containing heavy metals - is considered hazardous, according to Hungary's National Directorate General for Disaster Management (NDGDM).
While the cause of the deaths has not yet been officially established, the victims are thought to have drowned.'Desperate effort'
Some 600,000-700,000 cubic metres (21m-24m cubic feet) of sludge escaped from the plant, 160km (100 miles) from the capital, Budapest, affecting an area of 40 sq km (15.4 sq miles).
Environment Minister Zoltan Illes told the BBC the clean-up would take at least one year and probably require technical and financial assistance from the European Union.
He described the spill as Hungary's worst chemical accident.
in BBC World
