Authorities have confirmed that around 1,400 people have been evacuated from their homes in Germany.
This occurred after a chemical accident at a factory run by US food giant Kraft caused a cloud of poisonous gas.
The accident, at the small town of Bad Fallingbostel, near Hanover in northern Germany, happened on Monday when employees accidentally poured acid into a tank containing sodium hydroxide solution, causing a chemical reaction.
Some 700 firefighters were still trying to cool the container on Tuesday amid rising temperatures and fears of a possible explosion. Technical experts were trying to pump out the acid.
Local authorities have imposed emergency measures, including closing local schools and nurseries as well as parts of a major motorway running nearby. An exclusion zone of 500 metres (yards) has been set up.
A spokeswoman for the company said that no one had been injured so far.
"There has at no time been any danger for the population because we decided, along with the authorities, to evacuate as a precautionary measure," Heike Hauerken told rolling news channel N24.
Production was halted as soon as the accident took place, she added.