Hundreds of thousand of pills containing a powerful drug used to tranquilize large animals like elephants and rhinoceroses were seized by federal authorities in an operation last month in Los Angeles County.

What was described as a massive cache of carfentanil -- 628,000 pills -- were seized in the U.S. Drug Enforcement Administration operation, the agency announced Wednesday.

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Most of the pills, displayed in plastic baggies in a photo provided by the DEA, were seized from one LA County stash location. One person was arrested on suspicion of drug trafficking.

Details about the location and the individual's identity were not immediately available.

The synthetic opioid has veterinary uses, but has made its way onto

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