Earlier on Monday night, City Councilwoman Adriana Rocha Garcia referred to the victims as immigrants after the San Antonio Police Chief explained the situation.
Authorities were alerted to the scene just before 6 p.m., when they heard a worker in a nearby building crying for help, San Antonio Police Chief Phil McManus told a news conference Monday night. The worker found a trailer with the doors partially open, and found several people dead inside, McManus said.
San Antonio Fire Chief Charles Hood said 16 people – 12 adults and four children – had been taken to a nearby medical facility for further care.
Survivors suffered from heat to the touch, heat stroke and fatigue, Hood said, and they were unconscious when taken for care. There was no sign of water in the refrigerated tractor trailer and no working air conditioning unit was visible, he said.
Authorities hope those who were taken for treatment will recover. A Methodist Healthcare spokeswoman said three of the detectives were taken to Metropolitan Hospital Metropolitan and are in stable condition.
McManus said three people are in police custody, but it is not clear if they were involved in the situation.
A spokesman for Immigration and Customs Enforcement said Monday that the U.S. Department of Homeland Security’s intelligence unit has been alerted by San Antonio police to a “human trafficking incident” and is leading an investigation.
The 60 firefighters at the scene have been put under pressure by a major incident, Hood said.
“We should not open a truck and look at the layers of bodies there. Imagine that none of us come to work,” the fire chief said.
“It’s sad,” Mayor Nienberg said Monday. “We know, 46 people are not with us, have families, are trying to find a better life. And 16 of us are fighting for their lives in the hospital.”
The Consul General of Mexico in San Antonio said on social media that help would be given to anyone and all Mexicans. At least two of the 16 survivors have been identified as Guatemalaians, citing Mexico’s foreign ministry embassy.
The move is based on previous attempts to track down the smugglers who depend on them when migrants often cross the border. Last spring, the DHS also announced an effort with federal allies to crack down on criminal trafficking organizations.
CNN’s Carolyn Sung, Priscilla Alvarez, Michelle Watson, Karol Suarez, Sharif Paget, Jen Deaton, Amanda Jackson and Steve Almasy contributed to the report.

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