At least 54 people have been killed and scores more injured after the truck they were being transported in crashed in southern Mexico on December 10, 2021.
More than 150 people, said to be migrants from Central America, were crammed into the truck's trailer when it rolled in the state of Chiapas.
One resident heard a man implore his badly hurt companion: "Remember what you promised your mother! Hold on."
Pictures show victims strewn across the road next to the overturned truck.
Sabina Lopez, who lives nearby and ran to the scene after the crash, told the AFP news agency that she saw dozens of people screaming in pain, some trapped in the wreckage and others unconscious.
"It was horrible to hear the wailing. I just thought about helping," Ms Lopez, 18, told AFP.
She said the impact of the crash had broken the container in half and ripped off its roof.
Isaias Diaz arrived 15 minutes after the crash and helped paramedics with those people showing signs of life.
"I saw five, six children who were clearly injured. People with broken legs, ribs, [injured] heads, cuts on their necks," he told AFP.
"The crying, the pain, the despair. It was a terrible scene," he added.
Residents offered crash survivors water and mobile phones to contact relatives. They also said the driver and a person with him appeared injured, but then fled.
It is one of the worst accidents of its kind in Mexico. Forty-nine people were confirmed dead at the scene and five more died in hospital, Chiapas Governor Rutilio Escandón said.
Some 105 people - 83 men and 22 women - were also injured in the crash, he said.
Emergency officials said the victims included men, women and children. Most of the people on board were from Guatemala, but there were others from Honduras, Ecuador and the Dominican Republic.
The truck was reportedly speeding when it flipped on a sharp bend and hit a pedestrian bridge on a main road leading to the Chiapas state capital, Tuxtla Gutiérrez, at about 15:30 local time on Thursday.
Chiapas, which neighbours Guatemala, is a major transit point for undocumented migrants.