My question is in regards to K-9's used by law enforcement such as police, Customs, Department of Agriculture, etc. I'm aware K-9's have a sense of smell hundreds or thousands of times more sensitive than a humans, and different agencies use them to their advantage in aiding their find of drugs, explosives, agricultural products.
My question is are the dogs used by these agencies cross-trained in alerting to different scents? For example, are the dogs used by police and customs in airports generally only trained to search for explosives? Or are these K-9's usually cross-trained so that they can be used to recognize other scents as well, such as drugs and agricultural products?