Bulgarian prosecutors have charged six people over the deaths of 18 Afghans who suffocated in a truck abandoned near the capital, Sofia. The bodies were found inside a vehicle on Friday, in the deadliest incident linked to people-smuggling in Bulgaria as the country struggles with a rise in illicit border crossings. The truck was transporting 52 Afghans hidden under wooden planks and packed “like in a tin can”. The group had arrived from Turkey and was heading toward western Europe via Serbia, initial investigations showed. The 18 victims died from suffocation. Six Bulgarians, including the alleged ringleader of the smuggling group, were charged on Saturday, Hristo Krastev, a spokesperson for the Sofia public prosecutor’s office, told reporters. They face up to 15 years in prison if convicted on charges of involuntary manslaughter and participating in organised crime and people-smuggling. One of the suspects remains at large and was charged in absentia, while two others who had been arrested are not expected to be charged. Investigators say the truck’s drivers heard loud noises and knocks coming from the back but only stopped later, when they discovered the dead victims and fled, deputy attorney general Borislav Sarafov said. “The people transported were curled up and pushed against each other like in a tin can … They died slowly and painfully for 30 to 60 minutes. It is an extraordinary human tragedy,” Sarafov told reporters. Some of the 34 people who were rescued remain in hospital, with some being treated for carbon monoxide poisoning after inhaling exhaust pipe gases. The victims, believed to be aged between 13 and 35, had paid up to 7,000 euros each to the smugglers, Sarafov said. “It was out of greed that the smugglers carried 52 people. They had previously transported between 25 and 35 people at a time, at least twice a month,” he said. The hiding places were lined with aluminium foil to make the presence of people undetectable to thermal cameras, he added. Bulgaria, an EU member that serves as a gateway for many people hoping to enter the bloc, has been trying to tighten security to halt the rising numbers seeking to cross its southern border with Turkey. The Balkan nation has also faced accusations of abuses by security forces trying to stop people from entering, with asylum seekers saying they have been pushed back, locked up, stripped and beaten. Bulgaria has denied the allegations.