The toxic red sludge released from an industrial plant in Hungary has reached the Danube river.

The Prime Minister of Hungary Victor Orban called the spill an “ecological tragedy”. The sludge was caused as a result of an accident at an alumina plant in Ajka in western Hungary.

Nearby villages were damaged and vast areas of farmland have been destroyed. Four people have been killed and over 100 injured, mainly those working in the emergency services who have suffered from chemical burns.

The victims drowned in the fast flowing river of sludge, which reached a depth of 6.5ft (2.0m) in places. All life in the Marcal has according to Disaster expert, Tibor Dobson, been “extinguished”.

Countries downstream from one of Europe’s longest Rivers are already having to make emergency plans. South of Hungary, the 1,775-mile (2,850-kilometer) long Danube flows through Croatia, Serbia, Romania, Bulgaria, Ukraine and Moldova before reaching the Black Sea.

The sludge is a by-product from turning bauxite into alumina. The flood was caused because a dam holding the sludge burst.

There are also dangers arising from the drying of the sludge, if the sludge dries, the particles from it could become air-born. ITN reports that the sludge is also slightly radioactive, therefore increasing the risk of lung cancers.

MAL Zrt, the owner of the plant, issued a statement Tuesday saying that, “The red sludge waste is not considered hazardous waste according to EU standards,” and that it conforms to all safety standards”.

Gergely Simon of the Clean Air Action Group (CAAG) says his group has been trying to raise awareness since 2003 about the potential dangers of storing the slurry that comes from processing alumina, the material in aluminum, in open reservoirs. Unfortunately, he says, such storage is commonplace across Hungary.”The storage reservoirs are open so the water got in there and made what should have been a paste into a liquid,” says Mr. Simon. “Locals were reporting that the winds were making huge waves [inside the reservoir].”