Police said a chemical byproduct, high purity dicyclopentadiene, had been released into the atmosphere from the plant in the town of Wülfrath, mixing with rain and humidity to create an oily substance.
Twenty-five people exposed to the leak complained of a burning sensation on their skin and in their eyes and throats and received treatment. A wide perimeter around the plant was evacuated. A police spokesman from the German state of North Rhine-Wesphalia said the environmental impact of the mishap was not immediately clear although it seemed only a small area had been exposed to the gas.
On August 23, 107 people took ill after being exposed to a toxic leak from a lacquer factory in the western city of Mönchengladbach. The cause of the incident was believed to be a fault in the factory's automated fire extinguisher system which was triggered after a small fire broke out, police said.