E-cigarette liquid bought on Tyneside contained a potentially harmful chemical, a BBC investigation found.
Inside Out bought four liquid refills and sent them to a laboratory for testing. Three were clear but a fourth contained a chemical called diacetyl.
It is used as a flavouring in foods and experts said while it was safe to eat it was not safe to inhale and had been linked to a serious lung condition.
VIP, which distributed the refill, said it had been withdrawn from sale.
The four samples were bought in shops and markets and were sent for testing at a food control laboratory in Leeds.
The refill found to contain diacetyl was VIP's butterscotch flavour and was bought at its shop at the Metrocentre, in Gateshead.
'Popcorn worker's lung'
Lab analyst Chris Hunt said: "It's a flavouring. It's used in foods, it's used in margarines, popcorn and a number of other food products.
"But it has this property that although it is safe to eat it is not very safe to inhale."
Dr Graham Burns, a respiratory physician at Newcastle's Royal Victoria Infirmary, said diacetyl is associated with a lung condition called popcorn worker's lung.
"It has been inhaled in significant quantities in people who worked in popcorn manufacturing factories," he said.