The head of the emergency operation Boris Žnidark said nearby residents were told to close their windows as there was a danger of an expansion of the acid container at the glassworks in the eastern town of Rogaška Slatina, which could have led to a poisonous, corrosive cloud in the nearby area. 350 workers, who were evacuated earlier today, later returned to their positions. More than 50 firefighters participated in the emergency operation.