By Anastasia Moloney

BOGOTA (Thomson Reuters Foundation) - Migrants from Central America making the overland journey through Mexico are seeking out new, hidden routes to evade deportation, putting them a greater risk of being trafficked, experts say.

Rampant gang violence, poverty and few jobs, drives tens of thousands of people every year from El Salvador, Honduras and Guatemala - countries with the world's highest murder rates - to seek refuge and a better life mainly in the United States.

"Migrants, particularly those coming from Central America, can easily fall into the hands of traffickers," said Christopher Gascon, head of the International Organization of Migration's (IOM) mission in Mexico.

As authorities in the United States and Mexico beef up security and police patrols along their shared border to stem the flow, increasing numbers of illegal migrants are being deported back to Central America, Gascon said.

Until recently, many migrants would board freight trains in Mexico known as "La Bestia" or The Beast heading to the U.S. border, following well-established migrant routes along the railway tracks.

But the clampdown on migrants has meant they have sought out new, and more hidden, paths to cross through Mexico, putting them in greater risk of being trafficked.

"To avoid being deported, migrants are traveling more in new and less frequented routes, avoiding authorities, which means they are less visible and more vulnerable," Gascon said.

"Migrants are finding news routes we don't know about, traveling through forest and paths on foot and then on public transport. This is of great concern to us as we are unable to reach them and provide assistance."

It is common for Central American migrants to be approached by traffickers offering them false promises of work as they take a break in parks and squares during their journey across Mexico.

"Migrants are stopped and coerced befriended by traffickers, in many cases women," Gascon told the Thomson Reuters Foundation in an interview.

Experts say women and girl migrants from Central America, particularly those from indigenous groups, are particularly at risk of being trafficked into sex work in brothels and bars along Mexico's border with Guatemala.

Mexico's state of Chiapas, a poor region on the country's southern border with Guatemala, is a trafficking hotspot.

The porous border sees a high and constant flow of migrants heading north.

"A lot can be done at the border with border patrols by spotting victims of human trafficking by how a person is acting, reacting and who they are traveling with," Gascon said.

"We need to work more on the identification of victims. They slip through."

INCREASE CONVICTIONS

Mexico says it has made important steps to tackle human trafficking, including a 2012 anti-trafficking law that punishes those convicted of the crime to up to 30 years in prison, a special prosecutor's office in Mexico City and a free hotline.

Despite these efforts, prosecutions for human trafficking remain low in Mexico, as they do worldwide, in an industry the United Nation's International Labour Organization estimates is worth $150 billion a year.

Of the 621 preliminary cases of human trafficking brought forward in Mexico in 2014, only 156 resulted in a conviction, which means many trafficking victims do not get justice.

As part of efforts to boost conviction rates against human traffickers the IOM is providing training to Mexican judges across the country on the 2012 anti-trafficking law and cases.

So far the IOM has trained 200 judges and magistrates across Mexico, including those in the Chiapas state, and aims to reach 950 judicial officials by the end of the year, Gascon said.

"We are trying to get a common understanding across the county on how to approach human trafficking cases among all judges," he said. "There can be confusion about prostitution, exploitation and human trafficking."

A key challenge is also to ensure prosecutors are better prepared to investigate human trafficking cases, gather evidence and bring cases successfully forward to get convictions.

"There is a qualitative leap that needs to be made in order for prosecutors to know what is needed in terms of evidence to get convictions for human trafficking cases," Gascon said.

(Reporting by Anastasia Moloney, editing by Ros Russell.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit http://news.trust.org)