Zoltan B., the former CEO of MAL Zrt., received a prison term of two and a half years for public endangerment and other crimes, while Jozsef D., a deputy CEO, received a two year sentence.
In keeping with privacy rules, the court did not identify the defendants by their full names.
Eight other people on trial for the 2010 disaster received suspended prison sentences, fines or reprimands, while the city court in Gyor acquitted five.
The trial court ruled that MAL Zrt. managers and employees broke numerous rules regarding the storage and handling of the leftover sludge and water from producing alumina, the main raw material for making aluminium.
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"The defendants' negligence contributed to the catastrophe, since they did not deal with the warning signs of a possible breach," the court said in a statement.
"And they misled area residents and authorities regarding the true amount and toxicity of water accumulated due to the rule violations, which ultimately became determinant factors of the catastrophe."
The court also said the defendants did not notify authorities or were late doing so regarding the sludge flood and its toxicity.
The former CEO also made wilfully misleading statements about the dangers of the spill, the court found.
The amount of water stored in the 25-hectare (61.8-acre) reservoir, over 1 million cubic metres (264 million gallons), was more than twice the limit and its toxicity exceeded the permissible level.
In its ruling Monday, the court also faulted poor planning, construction and maintenance of the reservoir.
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Hungary sludge flood
On October 4, 2010, a wall of a huge reservoir of the plant collapsed, flooding three towns and villages with about 2 million cubic metres (528 million gallons) of toxic red sludge and water.
The highly alkaline mix burned the skin of the victims, some of whom were swept away by the force of the rushing flood and drowned.
One of the victims was 14 months old.
