Rats with super-sensitive noses that can sniff out landmines are being developed in the US by military-funded researchers.
The project was approved after scientists created genetically modified "super-sniffer" mice that can be programmed to detect specific smells.
In laboratory experiments, the mice were given DNA that heightened their sensitivity to a sweet-smelling chemical and tiny traces of an unpleasant odour they tried to avoid.
Now the team from New York City University has received funding from the US Department of Defence to develop rats with the same ability that can detect explosives and potentially uncover landmines.
Other possible spin-offs from the research include a "nose-on-a-chip" that can diagnose diseases from their smell.
The scientists, led by biologist Dr Paul Feinstein, wrote in the journal Cell Reports: "We have produced biosensors with an enhanced inherent sense of smell, which can be applied to address global health and safety challenges such as identification of explosives, contraband searches, and odour-based disease diagnosis."
Mammal noses contain a large collection of sensory neurons, each equipped with a single chemical sensor or "receptor" that detects a specific smell.
Collectively, the neurons have an even distribution of receptors sensitive to a broad range of odours.
The experimental mice have extra copies of a particular selected receptor, making them especially sensitive to a single smell.
In one behavioural test, animals with heightened sensitivity to an unpleasant odour were observed avoiding the smell in water.
They were able to detect far fainter traces of the odour than mice without super-sniffer abilities.
"The animals could smell the odour better because of the increased presence of the receptor," said co-author Dr Charlotte D'Hulst, also from New York City University.
The researchers said they had founded a company called MouSensor to commercialise the genetic engineering technology.
Their laboratory had also received funding from the Department of Defence "to develop super-sniffing rats that can be trained to detect TNT and potentially find land mines".