An international gang suspected of smuggling up to 40,000 stolen phones from the UK to China over the past 12 months has been dismantled by police in London. The criminal network is allegedly responsible for up to 40 percent of all phones stolen in the city during this period, according to the Metropolitan Police service, which described the crackdown as its “largest ever operation to tackle phone theft in London.”

BBC News reports that the investigation was launched last year after a victim traced their stolen iPhone to a warehouse near Heathrow Airport, which was discovered in a box containing around a thousand iPhones being shipped to Hong Kong. The intercepted shipment led to “significant arrests” and the recovery of stolen devices, according to the police announcement, with phone theft down by 14 percent in London so far this year.

“This group specifically targeted Apple products because of their profitability overseas,” Detective Inspector Mark Gavin said in a statement. “We discovered street thieves were being paid up to £300 (around $403) per handset and uncovered evidence of devices being sold for up to $5,000 in China.”