sniffer

Spanish emergency services said several crews - with drones and sniffer dogs - were deployed to look for those missing after Tuesday's collapse.

One of the boys allegedly walked past the offices of Europol, Eurojust and the Canadian embassy in The Hague carrying a "wi-fi sniffer" - a device designed to identify and intercept wi-fi networks.

But it is this strong smell, as well as the smell associated with their insect poo - frass - that makes them ideal to be found by sniffer dogs.

Out back, it looks almost empty – until a sniffer dog finds stacks of illegal cigarettes and tobacco inside a makeshift wall.

One officer is said to have been so upset by the decision to call off the hunt for bodies that he returned with sniffer dogs to make an unauthorised search of the area.