Royal Mail, operator of Britain’s main postal service, said on Wednesday it had banned the delivery of Samsung Electronics’s Galaxy Note 7 smartphones through its network for safety reasons, making it potentially difficult for many Britons to return the recalled devices.

Samsung ssnlf recalled about 2.5 million Note 7s last month after reports some had caught fire due to faulty lithium batteries, and the company said on Tuesday it would stop making the devices after fires were reported in replacement phones.

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Royal Mail said the ban also applied to its Parcelforce U.K. and international courier service.

For the latest on Samsung’s future after the Galaxy Note 7, watch:

The company said it would ask customers to detail the contents of their packages to ensure that hazardous items such as faulty lithium batteries were not transported.