GUADALAJARA, Mexico (AP) — Mexican troops have made a historic seizure of 15 tonnes of pure methamphetamine in the western state of Jalisco, an amount equivalent to half of all meth seizures worldwide in 2009.

The sheer scale of the bust announced late yesterday in the western state of Jalisco drew expressions of amazement from meth experts. The haul could have supplied 13 million doses worth over $4 billion on U.S. streets.

“This could potentially put a huge dent in the supply chain in the U.S,” said U.S. Drug Enforcement Administration spokesman Rusty Payne. “When we’re taking this much out of the supply chain, it’s a huge deal.”

Reporters were shown barrels of white and yellow powder that were found in a laboratory on a small ranch outside of Guadalajara, Mexico’s second-largest city.

The Mexican army said troops received several anonymous tips and found the massive drug stash in the township of Tlajomulco de Zuniga, near the Jalisco state capital of Guadalajara. The army statement called the seizure “historic,” implying it was the largest on record for the armed forces.

There were no people found on the ranch or arrests made, although it appeared 12 to 15 people worked there.

“Seizures of this size … could mean one of two things,” said Antonio Mazzitelli, the regional representative of the U.N. Office of Drugs and Crime. “On one hand, it may be a product that hasn’t been able to be sold, and like any business, when the market is depressed, stockpiles build up.”

Or, he noted, “such large-scale production could suggest an expansion, an attempt by some Mexican groups, the most business-oriented I would say, to move into Latin American and Asian markets.

The previous biggest bust announced by the army came in June 2010, when soldiers found 3.1 metric tonnes (3.4 tonnes) of pure meth in three interconnected warehouses in the central state of Queretaro, along with hundreds of tonnes of precursor chemicals used to make meth. A giant underground lab was also found in Sinaloa state.

Those other seizures were believed to be linked to the powerful Sinaloa cartel’s massive move into meth production. A senior U.S. law enforcement official in Mexico said Thursday this week’s bust in Jalisco was “probably Sinaloa.”

The official, who could not be named for security reasons, said Sinaloa may be moving into meth “to reduce its reliance on Colombian cocaine by flooding the market with meth.”

The size of the Jalisco bust stunned Steve Preisler, an industrial chemist who wrote the book “Secrets of Methamphetamine Manufacture” and is sometimes called the father of modern meth-making.

“I have never seen quantity in that range,” Preisler wrote. He also noted: “The amounts of precursors they were importing would produce multi-tonnes of product.”

There has also been a dramatic increase in seizures of meth-making chemicals imported to Mexico from countries such as China. Such seizures indicate that Mexico may become a world production platform for methamphetamines, and that Mexican cartels may be dominating the trade.