US authorities have arrested 76 people in a crackdown on drug smuggling from Mexico through Arizona after a 17-month probe, officials said. "Operation Pipeline Express" has broken up a "massive" trafficking network suspected of smuggling more than $33 million worth of drugs a month through Arizona's western desert, said Arizona Attorney General Tom Horne. "Today we have dealt a significant blow to a Mexican criminal enterprise that has been responsible for poisoning our communities with the distribution of millions of dollars' worth of marijuana, cocaine and heroin," he said. "I find it completely unacceptable that Arizona neighborhoods are treated as a trading floor for narcotics." The operation centered on the towns of Chandler, Stanfield and Maricopa, where backpackers and vehicles loaded marijuana and other drugs from the Arizona-Mexico border bound for a network of "stash" houses around Phoenix. After arriving in Phoenix, the contraband, which also included cocaine and heroin, was sold to distributors from multiple states nationwide. Last week federal and local investigators executed the third in a succession of large-scale enforcement actions tied to the probe, taking another 22 defendants into custody. Those arrested range from organizational "bosses" to stash house guards and load drivers. During last week's warranted searches, authorities seized more than two tons of marijuana, 19 weapons -- including assault rifles, handguns, and shotguns -- and nearly $200,000 in cash. "Through our joint efforts, we've sent a resounding message to the Mexican cartels that Arizona is off limits to their operatives," said Matthew Allen, special agent in charge for HSI in Arizona. "As this case makes clear, law enforcement in Arizona is united in its resolve to protect our communities and our country from the scourge of large-scale narcotics trafficking."