A third of the houses on the main street of this Bedouin town near Egypt’s border with Gaza look derelict, but inside they buzz with the activity of tunnel smugglers scrambling to survive a security crackdown by the Egyptian army.

Smugglers and tunnel owners, who once publicly advertised their services, have taken over the nearly two dozen single-storey concrete structures and boarded up their doors and windows to avoid the attention of the authorities.

While tunnels used by Gaza’s dominant Hamas militants to infiltrate Israel were a priority target of an Israeli offensive in the Palestinian enclave this summer, many smuggling conduits into Egypt have skirted detection. […]