Five "sniffer rats" have been in police training in the Dutch city of Rotterdam, learning how to distinguish between scents - including drugs and explosives.

The brown rats are due to go into active service next year, operating under the names Poirot, Magnum, Derrick - TV detectives popular in the Netherlands - and Jansen and Janssen, the Dutch names for the bowler-hatted detectives in Tintin.

It means the Netherlands will be the first country to use trained rats in civilian police investigations.

Anna Holligan reports.