Waste management firm Veolia has admitted purple smoke spotted coming from a chimney stack near Ellesmere Port emanated from its Bridges Road plant.
People travelling along the M56 at noon on Sunday witnessed the purple haze. Among them was Isabel Alonso, 29, from Chester, a passenger in a car on the Manchester-bound carriageway, who took photos on her mobile phone.
A Veolia spokesperson said: “On Sunday 8th June 2014, at approximately midday, a Veolia operative noticed a faint purple haze at our Ellesmere Port facility. This was caused by the type of waste being treated at the time.
“While this is a rare occurrence and we always endeavour to operate without a visible haze, there was no breach of our environmental permit and there was no risk to public health or the environment. It was treated and removed within minutes and as a matter of courtesy we have notified the Environment Agency.”