The chief executive of the industrial plant at the centre of the toxic sludge spill in Hungary has been taken in for questioning by police.
Eight people have so far died from the spill on 4 October near Ajka in the west of the country.
The red sludge has severely polluted an area of 40 square kilometres and spread into the region's waterways.
The arrest of Zoltan Bakonyi was announced by the Prime Minister Viktor Orban, the BBC reports.
Mr Orban also said the company would be temporarily nationalised and that those responsible for the disaster should bear the financial consequences.
About 150 people were also injured after up to 700,000 cubic metres of toxic by-product from the production of alumina burst from a storage reservoir.
Engineers and disaster relief workers, aided by volunteers, have been racing to finish an emergency dam to contain an expected second spill from the reservoir.