Mexico on Friday urged Washington to rethink its migration policy after a horror road accident killed 55 undocumented migrants in a truck on a major transit route to the United States.

Bodies draped in white sheets lined the roadside near Tuxtla Gutierrez in the southern Mexican state of Chiapas, where a truck transporting some 160 migrants -- most from Central America -- overturned Thursday.

Passengers, bleeding and with broken bones, lay in the road crying out in pain after the latest disaster to befall desperate people traveling through Mexico in search of a better life in the United States.

More than 100 people were injured.

Thousands attempt the long, often dangerous, and expensive journey every year to escape violence and poverty in their home nations in South and Central America.

Such tragedies, Mexican President Andres Manuel Lopez Obrador said Friday, should move the world to address "the underlying problem" -- despair.

"The migration problem cannot be solved by coercive measures, but by opportunities for work and well-being. People don't leave their villages for pleasure, they do it out of necessity," he said.

If the United States wanted to prevent migration to its shores, added Lopez Obrador, it should invest in social programs in Central America -- a matter he has discussed with Joe Biden.

But "there is slowness," said the Mexican leader.

The victims of Thursday's accident, authorities said, were from Guatemala, Honduras, Ecuador, the Dominican Republic and Mexico.

Most of the dead were from Guatemala, said Lopez Obrador.

"It was horrible to hear the wailing. I just thought about helping," 18-year-old Sabina Lopez, who lives nearby, told AFP.

The driver, who fled the scene, was allegedly speeding when he lost control of the truck.

The National Institute of Migration said it was working to identify the dead, pay for funerals and repatriate bodies. It said survivors will be allowed to stay in Mexico.