A leading French environmental group warned that October’s toxic mud spill in Hungary could cause long-term damage and called for a broad European effort to monitor its effects.

“We are concerned for the mid- and long-term,” Charlotte Nithart, the director of the Robin des Bois (Robin Hood) environmental group, said as it released a new report on the spill.

She warned against “turning the page” on the ecological disaster, which occurred when a holding reservoir at an alumina plant, some 160 kilometres west of Budapest, burst its walls on October 4.

The crack sent more than 700,000 cubic metres of toxic red mud spilling across an area of 40 square kilometres, polluting the Danube River and its tributaries and causing an ecological disaster.

Ms Nithart said pollutants would continue to spread in the region.

“The dry summer will see the peak period for dust, while in the winter the humidity encourages pollutants to spread,” she said.

The group has sent its 45-page report to the Hungarian government and the European Commission, she said, in the hopes of highlighting the need for better monitoring of toxic mud reservoirs throughout Europe.