The Biden administration vowed to hold human traffickers responsible for deaths of dozens of migrants in Texas.
Department of Homeland Security Secretary Alejandro Mayorkas said he was "heartbroken by the tragic loss of life."
Officials said at least 51 migrants died after being left in an abandoned tractor-trailer on a remote back road in the sweltering Texas heat.
They include over 20 Mexicans, seven Guatemalans and multiple people from Hondurans, according to Mexican officials.
Several others have been hospitalized, including four children.
It was the deadliest tragedy to claim the lives of migrants smuggled across the border from Mexico.
U.S. Rep. Henry Cuellar of Texas confirmed that the driver of the truck and two other people were arrested. The bodies were discovered on Monday afternoon on the outskirts of San Antonio when a city worker heard a cry for help from a truck parked on a lonely back road, the Associated Press reported.
Officers arrived to find a body on the ground outside the trailer and a partially opened gate to the trailer. Fire Chief Charles Hood said the survivors were dehydrated as no water was found inside the trailer.
"The patients that we saw were hot to the touch," Hood said. "They were suffering, from heat stroke, heat, exhaustion, no signs of water in the vehicle. It was a refrigerated tractor-trailer, but there was no, visible working AC unit on that rig"
Law enforcement said that at least 3 people were taken into custody, but they were not named as suspects in the matter.