Authorities seized more than 16 tons of methylamine, a chemical used to produce synthetic drugs, in the Mexican Pacific port city of Manzanillo, the Navy Secretariat said.

Attorney General's Office personnel, marines and SAT tax agency agents found the chemicals in a container aboard the Xin Yan Tai, a cargo ship that arrived from Busan, South Korea.

"In said container, personnel from the three agencies located around 640 25-kilo sacks which altogether weighed more than 16,000 kilograms of the mentioned substance," the secretariat said in a statement.

Methylamine, a psychotropic drug, is classified as a chemical precursor by federal law.

Ephedrine is among the substances made from this chemical.

Chemical substances used to produce synthetic drugs, such as ephedrine, are regularly seized by Mexican security forces.

Ephedrine and pseudoephedrine are used to manufacture methamphetamine, an illegal stimulant.

The shipment was turned over to the AG's office, which is handling the investigation.

Manzanillo, located in the western state of Colima, is Mexico's most important cargo port.

Mexico's biggest seizure of drug precursors was the confiscation of 839 tons in July 2011 at a warehouse in the central city of Queretaro, a bust that topped the previous record of 200 tons of precursors discovered in 2010 at the port of Manzanillo.

Mexico, which produces most of the crystal meth consumed in the United States, has imposed tight restrictions on the import of chemicals used to make illegal synthetic drugs.

Due to pressure from the security forces, some Mexican drug cartels have increased the production of synthetic drugs in Guatemala, analysts say.

Mexico's drug cartels are the main suppliers of illegal stimulants to the U.S. market.

The U.S. drug market has seen declining demand for cocaine and a simultaneous rise in demand for synthetic drugs, officials and analysts say.

Synthetic drugs are favored by users for their more prolonged effect and because they come in tablet form and are therefore considered "socially cleaner." EFE