The U.S. heroin market is entirely supplied from foreign sources of opium, say officials.
In addition to finding the puppies during the raid, agents discovered heroin concealed in body creams and aerosol cans, and pressed into beads, which were then sewn into purse linings and suitcases.
Using animals as drug couriers is nothing new, says Steve Robertson, a special agent at DEA headquarters in Washington, D.C.
Over the years, he says, drugs have been found inside cattle and even parrots.
Human drug couriers are used too. As depicted in the 2004 movie Maria Full of Grace, human "mules" ingest balloons or condoms filled with heroin, then retrieve the packets after they pass through the couriers' systems.
Drug traffickers "will go to any means, any length, to smuggle their poison up to the streets of America," Robertson said.
How many puppies the ring used as couriers is unknown. But one thing is certain: The canine couriers' fates were grim.
Robertson suspects the dogs would have been immediately killed and slit open on arrival in the U.S.
Luckily, that wasn't the case.
Colombian National Police officers have adopted three of the seized dogs. Other Colombian residents have taken in the remaining surviving puppies.
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