AT LEAST 54 people died and dozens were left injured on Thursday after a lorry packed with about 200 migrants crashed into the base of a steel pedestrian bridge in southern Mexico.

The victims were tossed and crushed in a pile of both the living and the dead when the trailer tipped over, eyewitnesses said.

Volunteer rescuers laid the most severely injured on plastic sheets on the road.

Ambulances, cars and pick-up trucks then transported them to hospitals.

Rescue workers who arrived at the scene first said that other migrants from the lorry had fled in fear of being detained by immigration agents.

One paramedic reported that some of those who hurried into surrounding neighbourhoods were bloodied or bruised but still limped away in their desperation to escape.

Survivor Celso Pacheco, from Guatemala, told the Associated Press news agency that the lorry had felt as if it was speeding and then seemed out of control.

Most on board were from Guatemala and Honduras, he said, estimating that there were eight to 10 young children among them.

Mr Pacheco said that he was trying to reach the United States but now expected to be deported to Guatemala.

Authorities said there also were migrants from Ecuador, the Dominican Republic and Mexico in the trailer.

The Mexican government is trying to appease Washington by stopping walking migrants and allowing the reinstatement of the Remain in Mexico policy.

But it has failed to address the flood of migrants stuffed in their hundreds into lorries operated by smugglers who charge thousands of dollars to take them to the US border.

Irineo Mujica, an activist who is leading about 400 migrants on a nearly six-month march across southern Mexico, blamed Thursday’s tragedy on Mexico’s crackdown on migrant caravans.

Mr Mujica and his group had almost reached the outskirts of Mexico City after weeks of dealing with National Guard officers who tried to block the action.

“These policies that kill us, that murder us, are what leads to this type of tragedy,” he said.

Mexico’s National Immigration Institute promised to offer humanitarian visas to the survivors.

Migrants involved in serious accidents are often allowed to stay in the country temporarily as they are considered to be witnesses to crimes.