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A recent U.S. drug bust shows that trafficking across the U.S.-Mexico border is a two-way street.

U.S. Customs and Border Protection agents in Los Angeles said Thursday they intercepted 520 pounds of a chemical used in illegal drugs like methamphetamine and ecstasy -- contraband caught not while it was coming into the United States from Mexico but while it was traveling south out of the U.S.

The meth component was being sent from China to drug traffickers in Mexico.

The chemical, methylamine hydrochloride, was discovered in August at an air cargo facility at Los Angeles International Airport, the agency said. Judging by the shipment's size, it could have produced 330 pounds of the drug methamphetamine.

It is hard to quantify how much money that methamphetamine could have fetched in the U.S., but a Drug Enforcement Agency representative estimated the street value between $6.6 million and $16 million.

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A spokesman from border protection said Mexican drug cartels have been growing desperate in recent months due to the increased enforcement on the U.S. southern border.

"This is a significant reflection of drug cartels getting frustrated because the traditional way of getting drugs in and out of the U.S. are not working," Jaime Ruiz, the spokesman, told FoxNews.com.

To be sure, border protection used the recent interception as an example of its widening reach at airports and seaports nationwide.

Todd C. Owen, a border protection field director in Los Angeles, called the interception a "fine example of the behind-the-scenes hard work" of the agency's officers to keep these chemicals from reaching drug trafficking organizations.

The eight drums of the chemical were discovered on Aug. 12. The agency sent the powder to a laboratory that identified the chemical.

The chemical has legitimate industrial applications in pharmaceutical products, but suppliers are subject to regulations and control measures, the statement said.

In August, authorities seized gamma-Butyrolactone at the airport. The chemical is used when manufacturing gamma-Hydroxybutrate, or better known as the date-rape drug, The Los Angeles Times reported. 

That shipment, too, was traced back to China, according to the report.

Mexico is the main source of methamphetamine in the United States. The drug has also become a scourge in Mexico's northern border cities like Tijuana, across from San Diego, and Ciudad Juarez, across from El Paso, Texas, The Associated Press reported.