At least 53 people have been killed after a lorry carrying as many as 200 migrants tipped over and crashed into a bridge in southern Mexico.
A further 54 people had been injured, 21 seriously, officials said.
Volunteer rescuers pulled people from the wreckage while the walking wounded were able to climb out from the twisted steel sheets.
The bodies of those who had died were laid in rows under white sheets by the road.
Rescue workers who first arrived said that there had been more people aboard the lorry when it crashed but many had fled for fear of being detained by immigration agents.
At least 650 people have died trying to cross the US-Mexico border this year. This crash was one of the worst single-day death tolls for migrants in Mexico since the 2010 massacre of 72 people by the Zetas drug cartel in the northern state of Tamaulipas.
It is not unusual for migrant smuggling operations in Mexico to overload many people into a vehicle.
The sheer weight of the lorry, combined with speed and a nearby curve, may have been enough to throw the truck off balance, authorities said.
Guatemalan President Alejandro Giammattei wrote on Twitter: “I deeply regret the tragedy in Chiapas state, and I express my solidarity for the victims’ families, to whom we will offer all the necessary consular assistance, including repatriation.”
The lorry had originally been a closed freight module of the kind used to transport perishable goods. The container was smashed open by the force of the impact. It was unclear if the driver survived.