By\u00a0Jaden Edison\u00a0and\u00a0Patrick Svitek\r\nSAN ANTONIO \u2014 A tractor-trailer found near Lackland Air Force Base in San Antonio contained the bodies of 46 dead people, along with 16 others who have been taken to hospitals, local officials in San Antonio said on Monday evening.\r\n\u201cThis is nothing short of a horrific human tragedy,\u201d San Antonio Mayor Ron Nirenberg said at a news conference near the scene.\r\nLocal officials said federal authorities were now investigating the case and that three people were in custody, but it was unclear if they were connected to the incident. A U.S. Immigration and Customs Enforcement spokesperson said Homeland Security Investigations is leading a criminal investigation with the support of San Antonio police.\r\nThe horrifying discovery was made near the intersection of Cassin Drive and Quintana Road in Southwest San Antonio.\r\nFederal, state, and local authorities believe that the victims were migrants. Cross-border smuggling and human trafficking have been longstanding problems along the U.S.-Mexico border, but the deaths of 46 people represent a stunning loss of life. San Antonio Police Chief William McManus described the case as the deadliest human smuggling incident he could recall in the city.\r\nAuthorities received the first call about the truck shortly before 6 p.m. from a worker in the area who had heard a cry for help and went to investigate, McManus said.\r\nAccording to a law enforcement official, it appears people were trying to jump out of the tractor-trailer because some of the deceased were found along several blocks. The tractor-trailer had a refrigeration system, the official said, but it did not appear to be working. Many of the people found inside the vehicle appeared to have been sprinkled with steak seasoning, the official said, in perhaps an attempt to cover up the smell of people as the smugglers were transporting them.\r\nAuthorities said the truck\u2019s doors were partly open when they arrived; a body was outside the vehicle and the rest could be seen inside. The city\u2019s fire chief, Charles Hood, said the survivors did not appear to have access to water and were too weak to exit the truck on their own.\r\n\u201cWe\u2019re not supposed to open up a truck and see stacks of bodies in there,\u201d Hood said. \u201cNone of us come to work imagining that.\u201d\r\nTwelve adults and four children were taken to hospitals. They were hot to the touch and were suffering from heat exhaustion and heat stroke, but Hood said he was \u201cvery hopeful\u201d that they would survive.\r\nWith a few days left in the month, National Weather Service meteorologists say June 2022 has already become the warmest June on record in San Antonio.\r\nThe average number of days with temperatures of 100 degrees or higher in San Antonio is nine, according to historical data from NWS dating back to 1885. This year, San Antonio has had 16 days with temperatures of 100 degrees or higher, NWS meteorologist Bob Fogarty said.\r\nMcManus told reporters that he was not confident that everyone who had been inside the truck had been accounted for and that authorities still don\u2019t have an indication of how many people in total had been inside the truck. He said the three people in custody were not found with the truck, but declined to comment further.\r\nMexican Foreign Minister Marcelo Ebrard said the Mexican consul in San Antonio was\u00a0en route\u00a0to the incident site, according to Reuters. Ebrard said the nationalities of all the victims were still unknown, but Guatemalan officials said in a statement that U.S. and Mexican authorities have confirmed some of the victims are from Guatemala. Officials with the Guatemalan consulate in McAllen said they are visiting a hospital to see if two of the children who survived are from Guatemala.\r\nThe Honduran foreign ministry said it is investigating whether any of the victims were from Honduras. Alex Selgado of Fuerza Catracha, a Honduran immigrant rights organization,\u00a0told The San Antonio Express-News\u00a0at the scene that \u201cofficials did inform us that some of the deceased may be Honduran because they had emblems or insignia of our country\u201d on their clothing.\r\nIn 2017, San Antonio police discovered 39 undocumented immigrants inside of a scorching-hot tractor-trailer, resulting in 10 deaths. The driver of the truck was sentenced to life in prison\u00a0in 2018.\r\nMeanwhile in 2003, 19 undocumented immigrants were found dead in Victoria after suffocating in an airless trailer.\r\nThe Rio Grande Valley Sector Border Patrol last week said it had disrupted four human smuggling events that resulted in 50 arrests.\r\n\u201cI am heartbroken by the tragic loss of life today and am praying for those still fighting for their lives,\u201d said Alejandro Mayorkas, U.S. secretary of Homeland Security. \u201cFar too many lives have been lost as individuals \u2014 including families, women, and children \u2014 take this dangerous journey.\u201d\r\nIn a tweet responding to the incident, Gov. Greg Abbott\u00a0blamed the deaths on President Joe Biden, saying that \u201cthey are a result of his deadly open border policies.\u201d\r\nDemocrat Beto O\u2019Rourke, who\u2019s running against Abbott for governor, tweeted that the incident is \u201cdevastating.\u201d\r\nGustavo Garc\u00eda-Siller, the Roman Catholic archbishop of San Antonio, wrote on Twitter: \u201cOnce again, the lack of courage to deal with immigration reform is killing and destroying lives. We do not learn. God teach us to change.\u201d\r\nThe Mexican consul general in San Antonio, Ruben Minutti, asked any Mexican citizens seeking help or information about the incident to call the consulate at\u00a0210-872-4386, according to\u00a0San Antonio Report.\r\nLomi Kriel contributed to this story. This story was originally published by the Texas Tribune.