Federal police Monday uncovered 4 tons of ephedrine in oil drums and boxes to be sent to Mexico and the United States.
The lead investigator called it the largest illegal shipment of the methamphetamine ingredient seized in Argentina and said it was worth millions of dollars.
The ephedrine, imported from India and China, was discovered with the help of U.S. and Interpol agents who have advised police investigating a group of Argentines and Mexican traffickers, Commissioner Miguel Castro said.
Castro said the boxes were hidden in a furniture warehouse and the drums were in another warehouse where one employee was arrested.
The chemical is worth $2,000 to $3,000 a pound on the street in Argentina, but the traffickers planned to ship it to Mexico, where it sells for five times as much, to gangs that make methamphetamine for sale in the United States, Castro said.
Investigators suspect the chemical had remained hidden after the execution-style killings of three Argentines, allegedly by Mexican hit men, in August 2008.
Two of the victims owned pharmacies that imported large quantities of the chemical, which is used in cold medicines, but allegedly intended to sell it instead to gangs from Mexico, which banned the substance in 2007.
Monday's discovery is the second this month. Four tons of properly declared ephedrine was found abandoned in a customs service depository in the port of Buenos Aires.