Phoenix --

Law enforcement officials on Monday announced the breakup of a massive drug-smuggling ring that used lookouts on hilltops in southern Arizona to move huge quantities of marijuana and other drugs across the Mexican border to users throughout the United States.

Over the last month and a half, federal, state and local officials have arrested 76 people, from organizational bosses to stash-house guards to those who transported the drugs in backpacks and in vehicles, the authorities said. All were linked to the Sinaloa cartel run by Joaquin Guzman, Mexico's richest and most wanted outlaw, who goes by the nickname El Chapo, officials said.

Speaking at a news conference on Monday, Arizona officials estimated that the ring had been in operation for at least five years and had generated more than $2 billion in profits by smuggling more than 3 million pounds of marijuana, 20,000 pounds of cocaine and 10,000 pounds of heroin into the United States. Such large smuggling rings usually use tractor-trailers to get their contraband across, the authorities said, but this operation relied mostly on migrants on foot.

The authorities acknowledged that the smuggling ring operated under their noses, albeit in rugged terrain that is difficult to patrol. Spotters with radios or cell phones were used to point out the presence of law enforcement and divert loads. The drugs would be carried in relatively small quantities and then transported north to a network of stash houses in the Phoenix area. From there, the contraband would be sold to distributors nationwide.

The route was through the most desolate desert areas of southern Arizona, from Yuma to just east of the border community of Sells, including the sprawling Tohono O'odham Indian reservation.

The investigation began in June 2010 with a traffic stop in Pinal County of a suspect who later provided details of the operation, said Sheriff Paul Babeu.

The authorities were reminded of how challenging the drug war had become when a federal grand jury in Tucson last week delivered an indictment charging a Border Patrol agent with accepting a bribe to let a truck that he believed was smuggling drugs and migrants past a checkpoint in southern Arizona. When the agent asked the driver if he was a U.S. citizen, the driver responded "buenos dias" and was waved through, officials said.