Sniffer dogs specially trained to find explosives have been brought in as part of counter-terrorism measures at Vancouver’s Winter Olympics.

More than 50 German shepherds specifically trained for security work will be at the Olympic venues, in addition to the dogs already working on Via Rail trains heading into the Olympic city.

Unlike airports, Canada's railways normally do not have extensive security measures. But the Olympics have led to a change in the rules, with regular inspections being conducted on trains and at stations.

Dogs will be involved in some cases, although sometimes only a physical inspection of travellers will be conducted.

According to the RCMP dog-training service the animals have been given specialized training to work in large crowds and to detect all explosive substances that could jeopardize the safety of the athletes and visitors.

Security measures unprecedented in Canada have been put in place in Vancouver for the Games that begin on Feb. 12. The security procedures will be discontinued at the end of March after the Olympic and Paralympic Games have finished.