BOGOTA (Thomson Reuters Foundation) - Zunduri, enslaved at a dry cleaners shop in Mexico City, was so thirsty at one point she blistered her mouth trying to drink steam from an iron, and was so hungry she chewed the polythene wrapping used to cover garments.
The 23-year-old Mexican woman, known only as Zunduri, told state prosecutors of her two-year ordeal after escaping last month, exposing one of the worst cases of slavery to come to light in the Mexican capital.
"It's almost unbelievable to think a person can be treated this way. It's one of the worst cases I've ever come across," said veteran prosecutor Juana Camila Bautista, who heads the Mexico City prosecutor's human trafficking office.
"Zunduri was chained, hit and tortured. She had 620 injuries on her body. Doctors said she has the body of an 81-year-old," Bautista told the Thomson Reuters Foundation in a telephone interview.
Seven people, including the female owner of the dry cleaning shop, have been charged with human trafficking and detained awaiting trial.
"We believe there is enough evidence along with the victim's testimony for those charged to get the maximum 30-year prison sentence for human trafficking," Bautista said.
Zunduri managed to escape and report the crime to police, but thousands of cases of slavery remain invisible.
The most common form of human trafficking in Mexico's sprawling capital of 20 million is carried out by gangs who force women and girls into sex work, Bautista said.
Victims of sex trafficking are paralyzed with fear and work under coercion in the city's bars, restaurants and massage parlors, and breaking down their frightened silence is the main challenge facing prosecutors.
"Human trafficking is an incessant and constant battle. It's a complicated crime that takes time to investigate," Bautista said. "The main barrier is the terrible fear victims feel that prevents them from coming forward and reporting the crime. They don't speak out. That's our biggest obstacle."
In the two years since the prosecutor's office was created, Bautista has overseen 350 operations against human traffickers, in which 400 victims have been rescued, and nearly half the 42 convictions for trafficking have been a result of tip-offs, often through the free national anti-trafficking hotline.
Despite such efforts, prosecutions for human trafficking remain low in Mexico, as they do worldwide, in an industry the International Labour Organization estimates is worth $150 billion a year.
Traffickers prey on poor, unemployed girls from the countryside and outside Mexico City who have little education and have often suffered sexual or other abuse at home, Bautista said.
"These girls are highly vulnerable and come from dysfunctional families. The traffickers seduce them, trick girls into thinking they are in love. They then get the girl pregnant and move them to the capital where they are sexually exploited."
The victims' fear stems from the traffickers' constant threats to harm their family and children.
"Traffickers make it clear to their victims that they know where their family lives. They take away their babies and threaten girls with never seeing their children again," Bautista said.
Prosecutors rely heavily on information from local residents to build a case against traffickers, she said.
Mexico is a "large" source and destination for forced labor and sex trafficking, with adults and children forced into sex work in tourist cities like Cancun and Acapulco, according to the U.S. State Department's 2014 Trafficking in Persons Report.
Organized criminal groups, some heavily involved in drug trafficking, also profit from smuggling Mexicans, including migrants making the overland journey to the United States, the report said.
".. official complicity, a lack of intelligence-based investigations, and some officials’ limited understanding of human trafficking continued to undermine anti-trafficking efforts," the report on Mexico states.
Bautista denies collusion in the capital between corrupt police and government officials and human traffickers.
"I haven't seen this type of complicity in Mexico City. Our work is transparent. Though we know organized crime groups exist in other parts of the country, they haven't permeated Mexico City," she said.
Reporting By Anastasia Moloney; Editing by Tim Pearce