Methamphetamine production has surged south of the border, from Baja California ranches to the highlands of Michoacán to the industrial parks here in Mexico´s second largest city, where authorities in January busted the largest laboratory ever discovered in the Americas.

The fortress-like compound ringed by high brick walls housed 11 custom-designed pressure cookers that could produce 400 pounds of the drug per day. It dwarfed anything ever found in California, where the standard cooking tool is a 23-quart beaker and a 20-pound batch is considered a good production day.

"It was the mother lode of mother lodes," a U.S. law enforcement official said.

The boom in Mexican methamphetamine production stems from successful efforts in the U.S. to control the sale of chemicals used to produce the drug, including the cold medicine pseudoephedrine.

Drug traffickers, some of them ex-convicts and fugitives from the United States, including a former chemistry professor from Idaho arrested last month, have resettled in Mexico because of the easy access to pseudoephedrine and other chemicals.

The largest share of the chemicals is believed to be shipped to Mexico from factories in China and India and routed through Hong Kong. China has emerged as the top concern for U.S. authorities.

Like traffic in heroin and cocaine, the methamphetamine economy has become a global phenomenon. So too is the battle to control what most U.S. law enforcement authorities consider the country´s greatest drug threat.

"The cliché is coming true: We´ve entered a new ice age," said Misha Piastro, an agent with the Drug Enforcement Administration who has worked on the U.S.-Mexico border, referring to the smokable form of the drug called ice.

The trend began surfacing about two years ago as a crackdown on the bulk distribution of ingredients cut off producers from supplies in the U.S and, later, Canada.

The rural fringes of California metropolitan areas, including the region just east of Los Angeles called the Inland Empire, which once were centers of methamphetamine production, remain important distribution hubs. But the number of "superlab" discoveries in California has dropped from 125 in 2003 to 12 through mid-October this year, according to the DEA. Nationwide, the numbers have dropped from 130 to 19 during the same period. Superlabs are operations that can produce more than 10 pounds of methamphetamine per cooking cycle.

Authorities now estimate that 80 percent of the methamphetamine on U.S. streets is controlled by Mexican drug traffickers, with most of the supply smuggled in from Mexico. Methamphetamine seizures at the U.S.-Mexico border have jumped 50 percent from 2003 to 2005, from 1,828 to 2,750 kilos.

Mapping the methamphetamine production network is difficult, in a country of remote ranchlands and under-patrolled metropolitan areas. Few law enforcement authorities are trained to recognize the signs of a drug lab, including the fumes and pollutants that pose significant environmental hazards.

Nonetheless, the number of labs discovered by Mexican authorities nearly tripled from 2002 to 2005, from 13 to 37, and methamphetamine seizures more than doubled, to 984 kilos, during the same period. U.S. authorities believe the numbers are a fraction of actual activity, as signs of an extensive production infrastructure have surfaced in the last year or so.

Among those signs: Mexico´s importation of cold medicines jumped suddenly in recent years, from 92,000 tons in 2002 to 150,000 tons in 2005. Although recently imposed restrictions have cut legal imports by about half this year, U.S. authorities believe significant amounts are still being smuggled through corruption-ridden Mexican ports.

Last December, Mexican authorities at the Pacific Coast port of Manzanillo found 5.1 million pseudoephedrine tablets hidden in a cargo of ceiling fans from China. The cache would have been enough to produce about 3 tons of finished product, authorities said.

Last November, China toughened its reporting and licensing requirements for enterprises manufacturing, shipping, trading and exporting bulk chemicals such as pseudoephedrine, a step welcomed by international drug enforcement officials.

But Beijing did not impose limits or reporting requirements on end users. Smugglers buy millions of cold tablets, hide these in Chinese export products and ship them to Mexico or other destinations, as seen with the ceiling-fan discovery.

China also faces problems similar to those in Mexico - budget constraints, corruption, turf battles and inadequate detection and monitoring equipment.

In Mexico, meanwhile, drug lab discoveries have spanned the country. In Mexicali, several labs have erupted in flames. In Michoacán, authorities have discovered large production operations and believe lab activity is rife in the state´s rural areas.

Producers also have flooded the Mexican domestic market with the drug, creating an epidemic of methamphetamine addiction and drug-related crime in many cities.

Guadalajara, capital of the western state of Jalisco, has emerged as a production hub for methamphetamine, authorities say. Lab activity is easily camouflaged in the metropolitan area of 4 million people, which encompasses isolated ranchlands, industrial areas and densely packed urban neighborhoods where exhaust and sewer smells mask the fumes of superlabs.

The ease of operating in Guadalajara vividly was illustrated in October, officials say, when authorities acting on an anonymous tip arrested Frederick Wells, a former Idaho State University professor who allegedly was running a superlab in his pink stucco home half a mile from the U.S. Consulate.

Wells, 57, who fled the United States in 1998 after being charged with operating a drug lab in his university office, had only to walk down the street to purchase industrial chemicals at a storefront business in Guadalajara. Authorities say Wells told them that neighbors in the quiet area of neat homes never noticed the smells during the nearly two years he operated the lab.

The enormous lab discovered in January was in a gritty area of chemical plants, small ranches and cornfields outside the city.

"We smelled things but didn´t know what it was. There are lots of factories around here; you never know what you smell," said Armando Murillo, who lives behind the former lab on a small ranch where he raises goats and sheep.

Murillo´s property was transformed into a campground for about 150 Mexican soldiers who guarded the lab for weeks. The suspects, a trio of chemists and former classmates at the University of Guadalajara, left behind more than 1,000 pounds of powdered methamphetamine in three barrels, and enough precursor chemicals to produce another 1,000 pounds, authorities said.

After the arrest of one suspect, authorities found four more superlabs they said were tied to the group. Another suspect is believed to have been killed by a local paramilitary-style gang, which is charged with burying alive five men at a ranch, one of them an ex-convict from California who had moved to Jalisco to get into the methamphetamine trade, a U.S. law enforcement source said.

Two other ex-convicts - one from California, the other from Phoenix - were arrested in August on suspicion of operating a lab at a ranch where Mexican authorities discovered 220 pounds of methamphetamine.

The migration south of fugitives and ex-convicts worries authorities who say it coincides with the release from U.S. prisons of many drug traffickers who have finished serving sentences dating from the early era of the methamphetamine trade.

With narcotics-related violence flaring across the country, experts say Mexico is ill-prepared to open another front against methamphetamine production. The DEA has donated equipment and begun to teach their Mexican counterparts how to find drug labs, but resources for a wide-ranging enforcement effort are scarce.

Authorities in Guadalajara, for instance, delayed dismantling the lab in January because the nearest lab truck, filled with protective suits and equipment to safely dispose of chemicals, was five hours away, in Mexico City.

"The problem is too new," said Marcos Pablo Moloeznick Gruer, a political science professor at the University of Guadalajara. He said Mexican law enforcement was not "aware or concerned enough" about the rise in methamphetamine production.