Another migrant died Tuesday at a local hospital, pushing the death toll of migrants found Monday inside a sweltering 18-wheeler in San Antonio to 51.Authorities said the tragedy in this major Texas city saw the highest ever death count from human trafficking near the U.S.-Mexico border.Among the dead, five were children. At least 27 were from Mexico, three from Guatemala and four from Honduras, local media reported, citing officials from these countries.Some of those found alive reportedly remained in critical condition Tuesday. After the truck packed with nearly 100 people was discovered on Monday, at least 16, including four children, were taken to area hospitals due to heat exhaustion and dehydration, local officials said."CLONED" TRUCKThe truck driver, who was caught in a nearby field after he fled on foot, and was described as a U.S. citizen, is now in federal custody and expected to be charged, San Antonio Police Chief William McManus told The New York Times on Tuesday.Two other men, both Mexican citizens, were charged on Tuesday with possessing firearms while residing in the United States illegally, according to court documents and U.S. authorities. Police arrested them at an address in San Antonio listed on the tractor-trailer's registration.The San Antonio Express-News reported that someone had "cloned" the truck with the same color and identifying numbers from the U.S. and Texas transportation departments as one owned by a South Texas trucking company in an apparent move to evade authorities.A vigil was held in the rain Tuesday evening at a San Antonio park."It's unspeakable," San Antonio Mayor Ron Nirenberg said on MSNBC Tuesday. "It's a tragedy beyond explanation."Those found alive were hot to the touch and suffering from heat stroke and exhaustion. There was no sign of water in the refrigerated tractor-trailer and no visible working air conditioning unit, according to San Antonio Fire Chief Charles Hood.Temperatures in San Antonio climbed to 101 degrees Fahrenheit (38.3 degrees centigrade) on Monday, while the heat in the packed trailer was likely way higher than that, according to the U.S. National Weather Service.FATAL BORDER CROSSINGU.S. President Joe Biden said Tuesday that initial reports showed that the tragedy was caused by smugglers or human traffickers."Exploiting vulnerable individuals for profit is shameful, as is political grandstanding around tragedy," Biden said in a statement, one day after Texas Republican Governor Greg Abbott blamed the deaths on what he called the president's "deadly open border policies.""My administration will continue to do everything possible to stop human smugglers and traffickers from taking advantage of people who are seeking to enter the United States between ports of entry," said Biden.The U.S. Customs and Border Protection said it encountered 239,416 people along the U.S.-Mexico border in May, hitting a record high.The Associated Press reported that migrants typically pay 8,000 to 10,000 U.S. dollars to be taken across the border, loaded into a tractor-trailer and driven to San Antonio, where they transfer to smaller vehicles for their final destinations across the United States.Death is a constant risk for undocumented migrants entering Texas, said a report by The Texas Tribune, noting that in 1987, 2003 and 2017, groups of migrants died of heat and dehydration in Texas after being trapped in stifling containers.According to the report, hundreds more die alone or in smaller groups as desperation drives them to take fatal risks.In 2017, 10 migrants died in a packed truck carrying 39 people in San Antonio during summer. In 2003, 19 migrants were found dead in a sweltering truck southeast of the city.Another migrant died Tuesday at a local hospital, pushing the death toll of migrants found Monday inside a sweltering 18-wheeler in San Antonio to 51.Authorities said the tragedy in this major Texas city saw the highest ever death count from human trafficking near the U.S.-Mexico border.Among the dead, five were children. At least 27 were from Mexico, three from Guatemala and four from Honduras, local media reported, citing officials from these countries.Some of those found alive reportedly remained in critical condition Tuesday. After the truck packed with nearly 100 people was discovered on Monday, at least 16, including four children, were taken to area hospitals due to heat exhaustion and dehydration, local officials said."CLONED" TRUCKThe truck driver, who was caught in a nearby field after he fled on foot, and was described as a U.S. citizen, is now in federal custody and expected to be charged, San Antonio Police Chief William McManus told The New York Times on Tuesday.Two other men, both Mexican citizens, were charged on Tuesday with possessing firearms while residing in the United States illegally, according to court documents and U.S. authorities. Police arrested them at an address in San Antonio listed on the tractor-trailer's registration.The San Antonio Express-News reported that someone had "cloned" the truck with the same color and identifying numbers from the U.S. and Texas transportation departments as one owned by a South Texas trucking company in an apparent move to evade authorities.A vigil was held in the rain Tuesday evening at a San Antonio park."It's unspeakable," San Antonio Mayor Ron Nirenberg said on MSNBC Tuesday. "It's a tragedy beyond explanation."Those found alive were hot to the touch and suffering from heat stroke and exhaustion. There was no sign of water in the refrigerated tractor-trailer and no visible working air conditioning unit, according to San Antonio Fire Chief Charles Hood.Temperatures in San Antonio climbed to 101 degrees Fahrenheit (38.3 degrees centigrade) on Monday, while the heat in the packed trailer was likely way higher than that, according to the U.S. National Weather Service.FATAL BORDER CROSSINGU.S. President Joe Biden said Tuesday that initial reports showed that the tragedy was caused by smugglers or human traffickers."Exploiting vulnerable individuals for profit is shameful, as is political grandstanding around tragedy," Biden said in a statement, one day after Texas Republican Governor Greg Abbott blamed the deaths on what he called the president's "deadly open border policies.""My administration will continue to do everything possible to stop human smugglers and traffickers from taking advantage of people who are seeking to enter the United States between ports of entry," said Biden.The U.S. Customs and Border Protection said it encountered 239,416 people along the U.S.-Mexico border in May, hitting a record high.The Associated Press reported that migrants typically pay 8,000 to 10,000 U.S. dollars to be taken across the border, loaded into a tractor-trailer and driven to San Antonio, where they transfer to smaller vehicles for their final destinations across the United States.Death is a constant risk for undocumented migrants entering Texas, said a report by The Texas Tribune, noting that in 1987, 2003 and 2017, groups of migrants died of heat and dehydration in Texas after being trapped in stifling containers.According to the report, hundreds more die alone or in smaller groups as desperation drives them to take fatal risks.In 2017, 10 migrants died in a packed truck carrying 39 people in San Antonio during summer. In 2003, 19 migrants were found dead in a sweltering truck southeast of the city.