June 27 (UPI) -- The bodies of dozens of people were found late on Monday inside and around a tractor-trailer abandoned on the side of a road just outside of San Antonio, authorities and officials said.
Sixteen people, including four children, were also found alive inside the trailer and were rushed to local hospitals suffering from heat stroke and exhaustion, city officials and authorities told reporters during a press conference.
"The plight of migrants seeking refuge is always a humanitarian crisis but tonight we are dealing with a horrific human tragedy," San Antonio Mayor Ron Nirenberg said. "We hope that those responsible for putting these people in such inhumane conditions are prosecuted to the fullest extent of the law."
The victims are believed to have been migrants who had crossed over the Mexico border into the United States though the authorities said they were unsure of their nations of origin.
San Antonio Police Chief William McManus told reporters that three people were in custody but it was unclear their connection to what he said was the largest death toll connected to a human smuggling case in the city that he could recall.
Authorities were called to scene shortly before 6 p.m. Monday. A worker at a nearby business had heard a cry for help and found the trailer with its doors partially opened. Inside, the worker saw the bodies, McManus said.
Responders with the San Antonio Fire Department were the first to arrive and found at least one body outside the trailer and several inside, Fire Chief Charles Hood said.
"We're not supposed to open up a truck and see stacks of bodies in there," he said. "None of us come to work imagining that."
There was no water inside the trailer, which was also a refrigerated truck but the air conditioning was not turned it, he said. It was also unknown how long they had been in the trailer.
According to the National Weather Service, the temperature on Monday hit a high of 101 degrees.
Hood said the 16 people alive were conscious but were "hot to the touch" and were "too weak" to exit the trailer on their own. No children were among the deceased, he said, adding that he was hopeful those transported to local hospitals would survive.
McManus also added that he is was not confident that everyone who was in the truck had been accounted for and police canines have been searching the nearby woods for survivors.
"Human smugglers are callous individuals who have no regard for the vulnerable people they exploit and endanger in order to make a profit," he tweeted. "We will work alongside our partners to hold those responsible for this tragedy accountable and continue to take action to disrupt smuggling networks."
The Mexican consulate was on the scene late Monday, Marcelo Ebrard, the country's foreign minister, said via Twitter.
Enrique Reina, the foreign minister of Honduras, tweeted that his office was investigating whether any Hondurans were among the deceased.
"They are a result of his deadly open border policies," the Republican governor tweeted from his personal account. "They show the deadly consequences of his refusal to enforce the law."
Meanwhile, Beto O'Rourke, a former House representative for Texas who is running for governor, called via Twitter for "urgent action" to dismantle human smuggling rings and "replace them with expanded avenues for legal migration that reflect our values and meet our country's needs."
The incident occurred amid surging encounters with migrants attempting to illegally enter the United States at the southwest border land border
According U.S. Customs and Border Protection data, 239,414 encounters were recorded last month, which is substantially higher than the 178,795 tallied a year prior.
Last week, CBP Commissioner Chris Magnus warned in a statement that as the temperatures rise, human smugglers will try to exploit the vulnerable "and recklessly endanger the lives of migrants for financial gain."
"The terrain along the southwest border is extreme, the summer heat is severe and the miles of desert that migrants must hike after crossing the border are unforgiving," he said. "Our message to those who would try and gain illegal entry to the United States remains the same -- don't make the dangerous journey only to be sent back."