More and more minors are making the long journey from Central America through Mexico and on to the US - alone.

Though these children are constantly threatened on their long journey, violence is nothing new.

In their home countries, criminal gangs target children and try to force them to join.

Such gangs operate with impunity throughout much of Central America - making it one of the most dangerous regions in the world.

Children have described body parts being left on their doorstep as a reminder that if they do not join, this is what could happen.

Experts say this is one reason why so many are fleeing - even while realising that the possibility they will not survive the trip is very real.

Females are the most vulnerable of these migrants and can face rape and kidnapping at the hands of drug cartels who frequently try to extort migrants, or worse.

Al Jazeera's Rachel Levin reports from Tenosique, Mexico.