San Antonio Fire Chief Charles Hood said at least 46 people were initially found dead inside the big rig, while 16 others, including four children, were hospitalized due to injuries, NBC News reports.
Mexican President Adrés Manuel López Obrador announced the death toll had risen to 50 on Tuesday (June 28), making it the deadliest human smuggling case of its kind in modern U.S. history.
López Obrador confirmed the casualties included 22 Mexican nationals, as well as seven from Guatemala and two from Honduras, while the nationalities of the other 19 individuals have yet to be confirmed.
San Antonio Police Chief William P. McManus said three people were taken into custody when police found the bodies inside truck, however, couldn't confirm whether the individuals were connected to the smuggling incident and didn't reveal their identities.
Authorities discovered the bodies inside the big rig early Monday (June 28) evening in an undeveloped area of San Antonio near rail road tracks after a person who works in the area told police they'd heard a cry for help and claimed to have seen at least one of the dead bodies in the area.
“We’re not supposed to open up a truck and see stacks of bodies in there,” Hood said via NBC News.
McManus said the surviving migrants were in need of water and air conditioning and were "suffering from heat stroke" and "heat exhaustion."