One of Mexico's most infamous cartels has invited a camera crew inside one of its industrial-scale methamphetamine labs hidden behind a taco stand for the first time.

After eight months of negotiation, the Sinaloa Cartel agreed to show Sky's Stuart Ramsay a "super lab" at work and with it an insight into the country's one billion dollar-a-year drug industry.

In Culiacan, situated in the central mountains, restaurants and taco stores act as fronts for the laundering of illegal drug money. Out the back they cook crack.

Inside one heavily-guarded lab, one of thousands scattered across Mexico, men in overalls and wearing gloves and face masks mix together a series of chemicals into huge drums.

There is an instant reaction, sending clouds of foul smelling, toxic and highly explosive gas into the air.

The reaction process only takes 15 minutes or so but to get to the point where they have created the meth will take a few days.

"Millions of dollars are made right here," the gang leader, who calls himself "Bull", tells Ramsay.

Even with 30 percent of his profits going towards bribes to police, government officials and other overheads such as guns for protection, Bull is still making $25 million a year profit.

"This is why people are fighting and killing each other," he says.

"Anyone else and you'd be dead."

Meanwhile, across town in another secret building 10 men in masks and gloves sit around tables laden with crystal meth.

For the next 48 hours they will pack the powder into tiny capsules before it is shipped abroad.

"It all goes to the US because it sells for more, the product goes directly to the United States," Bull says, adding that the value of the drugs increases nine times by the time they get to Europe.

"The majority of it is taken in trailers - that's how they take it from here."

Most experts who study the cartels believe it is unlikely they will be disposed of any time soon.

"They become a form of an alternative justice system or alternative police and that is very worrying for the country," Mexico-based British journalist and author Ioan Grillo said.