The nationalisation of the company came a day after police detained Zoltan Bakyoni, Magyar Aluminium’s (MAL) managing director, on suspicion of endangering lives and the environment.

MAL, one of Hungary’s largest companies, came under state ownership after parliament overwhelmingly passed a government bill resting the firm away from private ownership.

Under the new law the government can freeze MAL’s assets and appoint its own management until the investigation into the massive spill of toxic waste from one the company’s reservoirs is completed.

Nine people died when 1Mm3 of caustic slurry tore through three villages in western Hungary. It was caused by a breach in the bauxite residue containment area of the Ajka alumina refinery. The local environment was also devastated.

Bauxite residue material is the by?product of the Bayer process. Bauxite residue material is often described as red mud due to the colour of the original bauxite ore and the iron oxide it contains.

The residue normally has an elevated caustic content (ie a pH of between 10 and 12) although refineries try to recover as much caustic soda as possible during post?processing treatment to be able to reuse the material in the alumina production process.

The plant has been reopened after the Prime Minister, Viktor Orban, acknowledged the importance of the factory to its 1100 employees. He has said ‘human negligence’ was the cause of the disaster.