María Méndez was a live-in domestic worker when she met Ricardo López on her way to the supermarket. She was 15, from a poor family in the state of Mexico, and had been cleaning houses since the age of eight. He was a cocky, charming 16-year-old from Tenancingo, a small town in the neighbouring state of Tlaxcala. He courted her, promising marriage and a home. She desperately wanted it to be true, and within a fortnight moved with him to Tenancingo.

At first López and his family treated her well, but it quickly turned violent. “He sent me to work as a prostitute in Tijuana, Guadalajara, Torreón, Aguascalientes – all over the country to make money selling my body,” Méndez, now 59, told the Observer. “He said the money was to buy land so we could build a little house, but it was all false, even the name he’d given me was false. He made me live a very sad, ugly, desperate life. I was so ashamed.”

Méndez, like thousands of other vulnerable women in Mexico, was hoodwinked by a family of traffickers in Tlaxcala, the country’s smallest state just two hours east of Mexico City. This is a deeply religious place, where the indigenous Nahua people united with the Spanish to conquer the mighty Aztecs, but which over the past five decades has transformed into an unlikely hub of human trafficking.

In the US, five of the 10 “most wanted” sex traffickers are from Tenancingo, where Mendez’s nightmare began. Trafficking networks rooted in Tlaxcala are the biggest source of sex slaves in the US, the state department has said.

This improbable crime story began in the 1950s after industrialisation, when working-age men returned home from neighbouring states to find few opportunities beyond badly paid factory jobs. Pimping and trafficking, which they had seen while working away, was a way to get ahead, and many set up small, family-run sexual exploitation rings.

Some of the most powerful Tlaxcala families are believed to collaborate with Mexico’s most feared cartels.

In 2008 trafficking was detected in 23 of Tlaxcala’s 60 municipalities. By last year this had increased to 35, according to research conducted by local human rights group the Fray Julián Garcés centre, which has identified six “red zones” where sexual exploitation is most concentrated. (A government official told the Observer there were no red zones in Tlaxcala).

In Tenancingo, population 11,000, the presence of organised crime is breathtaking. Huge, tawdry houses are scattered among rows of ordinary, modest homes. Everyone knows who own the big houses, though, despite pressure from NGOs to improve transparency and target trafficking proceeds, there is no public land registry. The mansions look like fancy multilayered wedding cakes adorned with sculptured eagles, lions and swans. The grandiosity continues into the cemetery, where tombs are ornate and extravagant – not unlike those seen in villages of the northern state of Sinaloa, from where many of the drug cartel leaders hail.

In Tenancingo’s main square, a striking colonial church towers over taco stalls and shoe-shiners, a typical lunchtime scene apart from the new white Mustang and Chevrolet parked beside a bar. Here, a group of men in their 30s and 40s sporting designer jeans and T-shirts knock back cold beers under the piercing afternoon sun. Two police officers are stationed less than 150 metres away.

“These guys are the archetypal padrotes [pimps],” said Emilio Muñoz, a Tlaxcala native and director of human rights and gender violence at the Fray Julián Garcés centre.

“They are the ones who go to other states looking for vulnerable girls to trick – that’s their role in the family business. Everyone knows who the padrotes are, it’s no secret, and it’s the same families who sponsor religious festivals and community events. They operate with almost complete impunity. Trafficking has become so normalised and rewarding that young people look up to them.”

One in five children here wants to be a pimp when they grow up, according to a 2010 University of Tlaxcala study. Two-thirds of youngsters surveyed knew of at least one relative or friend working as a pimp or trafficker.

Tenancingo is the most notorious hotspot in Tlaxcala, with some estimates suggesting one in 10 people are actively involved in trafficking. But 16km north in Axotla del Monte, population 2,000, the concentration of garish mansions and flashy sports cars is even more conspicuous. This is another red zone, home to loyal, close-knit communities. In December 2012 the army was drafted in after police officers were almost lynched trying to detain an alleged trafficking family.

A street in Tenancingo, which has a population of about 10,000. Photograph: New York Daily News/ Getty

The old interstate highway connecting Axotla with Tenancingo is lined with cheap hotels. Official notices indicate a few recent closures, but many more are under construction. Around midday, young women wearing fake leather trousers and platform heels emerge near the hotels to attract the attention of passing motorists.

It is a wretched scene. The women’s features suggest they come from the poor southern states of Chiapas, Oaxaca and Guerrero, where a large proportion of trafficking victims originate, according to the United Nations Office for Drugs and Crime (UNODC). For most, Tlaxcala is only a pit stop until they are sent to more lucrative locations in northern Mexico and the US.

In recent years the modus operandi for trafficking throughout Mexico has shifted from kidnap and brute violence towards psychological deception and fake relationships. Poor, uneducated and often indigenous girls and women are dazzled and lured with the promise of jobs or marriage. Most commonly, as in Méndez’s case, women are initially persuaded to prostitute “for love”, in order to help resolve a financial crisis which the trafficking family feigns. By the time they realise and accept they are victims, their “husbands” use beatings and threats against their parents and children – often fathered by the traffickers – to control them.

“The few successful prosecutions have mainly involved international crime groups, yet most trafficking in Mexico occurs within close family and friends’ circles using rustic methods of seduction which are very difficult to investigate and prosecute,” Felipe de la Torre, UNODC adviser in Mexico, said.

US authorities have prosecuted several powerful Tlaxcala families, most famously the Carreto clan, who between 1991 and 2004 duped, coerced and trafficked Mexican women into prostitution in New York City.

It took almost 10 years for one victim, a woman from Guadalajara, to be reunited with her daughter who was left growing up within the Carreto family in Tenancingo.

“There is a lack of political will and legal sensitivity when it comes to reuniting victims with their children – who are at huge risk of being trafficked or absorbed into the crime family,” said Gretchen Kuhner, director of the Institute for Women in Migration.

The Tlaxcala government told the Observer that it has jailed 14 people for trafficking-related crimes since 2011 – around 10% of the national total. Authorities have rescued 127 trafficking victims, closed down more than 200 bars, nightclubs and hotels, and conducted hundreds of awareness-raising events, it added.

There are an estimated 20,000 trafficking victims in Mexico every year, according to the International Organisation for Migration. Tlaxcala has no refuge for trafficking victims.

Méndez endured 10 years of arrests, humiliation and threats, before finding strength through her faith to stand up to López and stop prostituting herself. “He beat me, threatened to take our children, but I stayed with him because of the shame. I couldn’t bear to tell my family the awful things I had done, or who my husband really was.”

They are still married, and live together near where the girls are forced to prostitute themselves on the highway. López works in a shop, though his extended family continue trafficking. Méndez added: “These men in their nice cars think money is more important than human dignity, but they are monsters, just like my husband. Sometimes when I see the poor girls I can’t breathe. I pray one day this town can come out of this.”

Names have been changed to protect individuals

This article was amended on 10 April to correctly place Tlaxcala east of Mexico City.

