E-cigarette company Juul Labs won a court ruling to stop stores on London's busiest retail street selling counterfeit versions of its products.

In a London hearing Friday, the vapemaker won an injunction stopping 10 stores on Oxford Street from selling fake Juul pods that contained illegaly high levels of nicotine. According to the company's court filing, it sent undercover agents to the stores to confirm that fake pods were being sold before trying to confiscate them.

Controversy over the safety of e-cigarettes is raging in the U.S., where the deaths of more than 50 people have been linked to a vaping-related respiratory illness. Health officials are studying whether the cause is vitamin E acetate, which is added to dilute THC, the euphoric compound in marijuana, in illicit e-liquids that that some vapers are using.

Juul is the industry leader in the U.S., having captured over 70% of the market, while in Britain just over a third of products sold are made by the company, which offers six different flavors of e-liquid.

In the shops, several of which doubled as souvenir shops, agents for Juul found pods containing almost three times the legal concentration of nicotine. The company said in its filing that there was no way of knowing what ingredients were in the e-liquid, which is vaporized and inhaled by the user.

Representatives for the stores weren't at the hearing on Friday. According to Juul's court filing, one of the shops owners claimed ignorance of any wrongdoing.

In its court filing Juul said that illegal and unregulated products bearing its branding were "highly damaging" to its reputation and to that of the industry as a whole. It also said the shops were unlikely to follow practices designed to prevent minors purchasing the products.

Neither Juul nor its lawyers responded to phone call seeking comment.