Colombian smugglers turned puppies into drug mules by surgically implanting them with packets of liquid heroin, authorities said.

Investigators believe the ring used the dogs, as well as people who swallowed the drugs, to conceal millions of dollars of heroin on commercial flights into New York for distribution on the East Coast.

Ten puppies, including Labrador retrievers, were rescued during a 2005 raid on a farm in Colombia, the U.S. Drug Enforcement Administration said Wednesday, while announcing more than 30 arrests.

A veterinarian had stitched a total of 3 kilograms of heroin into the bellies of six pups. Three died from infections after the drugs were removed.

The surviving dogs "are still alive and well, we're told," said John P. Gilbride, head of the DEA's New York office.

Colombian police said they adopted three dogs, one of which was being trained to sniff for drugs.

It was unclear how many dogs might have been used in the smuggling scheme, Gilbride said.

"I think it's outrageous and heinous that they'd use small, innocent puppies in this way," he said.

Besides the pups and human swallowers, authorities said the ring based in Medellin also concealed drugs in body creams, aerosol cans, and the linings of purses and luggage.

Recent raids in Colombia resulted in more than 20 arrests; another 10 suspects were in custody in New York, Florida and North Carolina. About 24 kilograms of heroin was seized, officials said.