The toxic Hungarian sludge flood was caused by the rupture of a red sludge reservoir at an alumina plant in western Hungary and has affected seven towns near Ajkai, 100 miles (160 kilometers) southwest of Budapest. The toxic red sludge killed seven nine people and caused over 120 injuries. This sludge is highly toxic and contains a mixture of heavy metals.
And below is some news footage including NASA images of the spill which shows the scale of the disaster.