Authorities seized more than 54 tons of monomethylamine, a substance used to produce designer drugs, in the western port city of Manzanillo, the Mexican Attorney General's Office said.

The chemicals arrived in four containers shipped from China, the AG's office said.

The biggest seizure of drug precursors made in Mexico occurred in August 2010, when 200 tons of banned chemicals were seized in Manzanillo.

Revenue service agents and navy personnel found the 320 barrels filled with monomethylamine, a colorless chemical.

Monomethylamine is listed as a psychotropic compound and a chemical precursor in Mexico, the AG's office said.

Mexico's Pacific coast, where Manzanillo is located, is a major area of activity for smugglers of chemical precursors and cocaine from South America.

Drugs are smuggled via the Pacific corridor or through central Mexico into the United States, the world's largest consumer of illegal drugs.