Explainer: Hungary's toxic sludge torrent

Matthew Knight
For CNN

(CNN) - A tide of toxic red mud burst through the walls of a giant storage reservoir at the Ajkai Timfoldgyar alumina refinery on the outskirts of Akja, a small town in the county of Veszprem, Hungary on Monday, October 4.

So far, four people are known to have been killed by the torrent, six people are missing and more than 120 people have been injured by the sludge which inundated the villages of Kolontar, Devecser and Somlovasarhely, around 150 kilometers southwest of the capital, Budapest.

According to Zoltan Illes, Hungary's Environmental Affairs State Secretary, around one million cubic meters of sludge has leaked from the reservoir covering over 40 square kilometers of land.

Illes described the flood as Hungary's worst chemical accident and an "ecological catastrophe."

Why did the reservoir wall break?

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