In 14 major coca-growing regions across the country, some 110,000 metric tons of coca is cultivated annually, and then turned into 180 metric tons of cocaine, according to government figures.
What is more worrisome to authorities here is that traffickers from other countries, principally from Mexico, have changed the face of the industry. Bypassing Colombian traffickers, Mexican cartels are working directly with farmers, demanding that Peru not only export the leaves or paste that is part of the process of synthesizing cocaine, but the cocaine itself.
It's a multibillion-dollar industry, which authorities say has given rise to corruption at all levels of society.
"For a while Peru's problem went down," says General Zarate. "Now again, we have this problem. There is an invasion of mafias in Peru."
Colombian rebels, he says, are vying for control along the border with Peru. But the bigger concern is Mexican-run cartels, he says, which have been active in the country for the past 15 years but have recently become more violent. "They have invested a lot of money to claim space here," Zarate says. "They are savage, and they pursue and pursue."
The slaying of the federal judge, Hernan Saturno Vergara, in July, was a wakeup call for many Peruvians about the grip of Mexican cartels, say observers. The judge had been overseeing a case involving alleged members of the Tijuana Cartel, and was gunned down while at a restaurant near his Lima office.
"It was a threat by these mafias to the entire judicial system," says Medina.
On a recent day, Medina stands in the back of a courtroom at the Callao prison in Lima, while a case involving three suspects charged with selling cocaine plays out. The case is one of an estimated 7,000 her department will hear this year – a number that has increased by 30 percent in the five years since Medina was named to the post.