At least 46 people have been found dead in the back of a truck in Texas.
The truck was found next to railroad tracks in the Southwest Side of the city of San Antonio.
Fire officials have confirmed that 16 people, including four children, were taken to hospital and are “hopeful to survive”.
It is believed the dead were migrants and San Antonio Police have confirmed that three people are in custody.
San Antonio fire chief Charles Hood said the truck was refrigerated but there was no water or air working air conditioning.
He said the patients were hot to the touch and suffering from heat exhaustion.
“We’re not supposed to open up a truck and see stacks of bodies,” he said. “Nobody comes to work for that.”
Mr Hood confirmed that no children are among the dead.
San Antonio police chief William McManus said a person working in a nearby building heard a cry for help and came to investigate.
The worker found the lorry door partially open and looked inside to find a number of bodies.
He said three people are in custody and a federal investigation has been launched.
A spokesperson for US Immigration and Customs Enforcement said its Homeland Security Investigations division was investigating “an alleged human smuggling event”.
The Secretary of Foreign Affairs for Mexico, Marcel Ebrard, said that a consul is on its way to the neighbourhood and that at least two of those in hospital were from Guatemala.
Temperatures in San Antonio, which is about 160 miles (250 km) from the Mexican border, hit a high of 39.4C on Monday with high humidity.