CIUDAD JUAREZ, MEXICO (AFP) - Mr Jose Mario Licona and his family spent 18 hours in a refrigerated truck being smuggled to the Mexican-US border - a journey he feels lucky to have survived.

Others have been less fortunate, including dozens of migrants from Mexico and Central America found dead on Monday (June 27) after being abandoned in a sweltering tractor-trailer in San Antonio, Texas.

In all, 53 people died in the incident.

Mr Licona knew all too well the dangers of entrusting his life to the criminal gangs trafficking migrants in trucks that are often overcrowded and lack ventilation.

But the smugglers - who were paid US$13,000 (S$18,100) by his relatives to take him, his wife and three children to Texas - left him with no choice, he said.

"When you make a deal, the first thing you ask (the smugglers) is not to be put in a container, but during the journey they do what they want," Mr Licona said in a shelter in the Mexican border city of Ciudad Juarez.

"Often, they leave the containers abandoned" with people shut inside, the 48-year-old Honduran said.

Mr Licona, his wife and children aged two, six and eight travelled in a truck from Mexico City to the north-eastern city of Reynosa, just south of Hidalgo, Texas.

Around 100 people were travelling in the same vehicle, which was not checked even once by Mexican authorities during the more than 1,000km journey, Mr Licona said.

From Reynosa, the family crossed the border on foot, but they were sent back by the US authorities.

'Criminal enterprises'

The smuggling networks operating the tractor-trailers are becoming increasingly sophisticated, said Ms Dolores Paris, a migration expert at the Colegio de la Frontera Norte.

"We're talking about criminal enterprises," she said.

The tractor-trailer involved in the San Antonio tragedy went through two immigration checkpoints in Texas and had cloned licence plates, according to the Mexican government.

Investigators are still trying to establish where the vehicle began its journey.

It was the second such disaster in the city in a little over five years. In July 2017, 10 migrants were found dead in an overheated truck that was discovered parked outside a Walmart supermarket.

In 2003, 19 migrants died in similar circumstances in Texas.

Mr Licona, a shopkeeper, left Honduras in May after he was shot in the arm during a robbery.

The trailer ride was so gruelling that he still regrets it, he said.

"It was very cold. I gave my children two pairs of pants, three shirts and a quilt. They slept during the journey. We brought hydration drinks for them, but I didn't want to wake them. Thank God we're here," he said.

The cold made his arm hurt more, but he endured it in the hope of reaching Texas.

After crossing over from Mexico, the family turned themselves over to a US border patrol in an unsuccessful attempt to gain asylum. They now hope to be given another chance to enter the United States on humanitarian grounds.

'Angel saved me'

Migrants staying in shelters near the Mexican-US border said the journeys last up to two days, with as many as 400 people crammed into a tractor-trailer like "animals".

Some undress or faint in the heat. Others avoid eating or drinking so they do not have to urinate. When the containers are refrigerated, it is like being in a "freezer", according to one young woman.

Around 6,430 migrants have died or disappeared en route to the US since 2014, according to the International Organisation for Migration. Of those, 850 were the result of vehicle accidents or linked to hazardous transport, the United Nations agency said.

In December, 56 US-bound migrants from Central America were killed and dozens injured when the truck they were travelling in overturned in the southern Mexican state of Chiapas.

Aware of the risks, a Honduran mother who gave her name as Jenny said she refused to get in a truck in south-east Mexico with her daughters, aged eight and 14.

Instead, they continued their journey without the traffickers, despite having been charged US$7,500 each.

"It was like an angel saved me," said the 32-year-old, who fled gang violence in her country and hopes to be granted asylum in the US on humanitarian grounds.

"Everyone has the right to have a chance," she said.