Four Mexican nationals were arrested on Monday in connection to a horrifying incident in which dozens of migrants being smuggled in a boiling-hot tractor trailer died in San Antonio, the U.S. Attorney's Office for the Western District of Texas announced. A grand jury indictment accuses Riley Covarrubias-Ponce, 30, Felipe Orduna-Torres, 28, Luis Alberto Rivera-Leal, 37, and Armando Gonzales-Ortega, 53, of participating in a human smuggling organization. The smugglers allegedly coordinated the transportation logistics, including obtaining the truck and handing it off to the driver, and knew the trailer’s air-conditioning unit was faulty. According to the indictment, they met with the truck at the end of its journey and found 48 migrants dead and 16 injured—five of whom later died at the hospital. They are charged with conspiracy to transport illegal aliens resulting in death, among other counts. If convicted, they all could face life behind bars. Last July, two men were indicted for the incident, including suspected driver Homero Zamorano and Christian Martinez.